TERRA MISSION

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Terra Status: May 5, 2000

The second of two inclination maneuvers was successfully completed late last week. Terra's mean local time is now slowly drifting towards 10:15am from its present value of approximately 10:47am. The next inclination maneuver will be three years from now when the mean local time reaches 10:15am.

(c) py5aal The first of a planned series of RF tests with the DSN was performed this week. These tests are directed at establishing that no RF interference issues exist between the MODIS direct broadcast service and the deep-space network. Direct broadcast service is now continuous around the earth, except for those periods above the three DSN stations.

An operations phase Deep-Space Calibration Maneuver Team has now been formed to analyze options for addressing the ASTER VNIR solar avoidance requirement. The team consists of Flight Ops Team, Flight Software Maintenance, GSFC AETD GN&C, and Terra sustaining engineering personnel. Of the eight options identified for changing the baseline deep-space maneuver, the team will initially focus on the two options which require minimal changes to the baseline deep-space maneuver. The team is presently in the process of identifying the failure scenarios which will then be simulated to assess compliance with the new ASTER VNIR solar avoidance requirement. Based on an agreement of the Terra Science Investigator leadership, the deep-space maneuver will be delayed for approximately one year.

(c) py5aal With the completion of last weeks inclination maneuvers, the activation of Terra has been completed. This week marks the final status report which I will be issuing to the above distribution. Since this distribution includes so many of the personnel responsible for this incredible mission,I wanted to take one last opportunity to congratulate and thank the people who made this great observatory possible. The spacecraft and instrument developers on this observatory took-on a staggering number of new development challenges, and the results being observed to date are nothingshort of astounding. The flight operations team can be proud of their extraordinary performance during the activation period, and their capabilities are reflected in the high level of confidence which the Terra partners have in them. The ground system folks should likewise be proud of their accomplishments managing an unprecedented data volume, and in their agility to continue to refine and improve the system.

(c) py5aal Unlike more modern approaches to project management, Terra was a true partnership between government and industry. In so many areas, contractors and civil servants collaborated, to both achieve the highest possible level of mission performance, and at times out of survival of the external factors that threaten the very core of this industry. Competition was replaced with collaboration. This is certainly not an original concept at GSFC, but one which played strongly in its success in the end. The ability to utilize all personnel on a single Terra Team, enabled the success of this mission, in the face of a multitude of external forces.

The technical capabilities and the dedication of the Terra partners has been compelling. The caliber of the people who worked this mission, will without a doubt, be the mostly lasting image I keep of this Project. I would like to wish each of you the best in your future endeavors, and I look forward to our paths crossing again, in whatever field the future takes us.

Kevin Grady

Preparations for a pair of spacecraft roll maneuvers were completed this week, and as this report was being sent, the first of the maneuvers had been successfully executed, with the second maneuver planned for later this afternoon. These small roll maneuvers position the moon in the space-view port of MODIS. Roll maneuvers will be performed every month for MODIS at the same point in the lunar cycle. This first set of roll maneuvers also serves as a calibration maneuver for the roll inertial measurement unit.

(c) py5aal Direction was provided from HQ this week on how to proceed with the MODIS direct broadcast service. Direct broadcast service will be limited to Hawaii, Australia and the east coast of North America for the next month.

This will allow the direct broadcast folks at Goddard to service a bounded set of inquiries from at least four additional users, based on the experiences they have acquired over the past few weeks. It will also allow an examination of any potential interference issues with the DSN (Canberra).

Plans are being made to test the realtime ASTER Direct Downlink (DDL) service the first week of April. The 105 mbps data will be captured on tape at Wallops, and shipped to Japan for processing.

Kevin Grady

(c) py5aal As Terra reached the Launch+90 Day milestone, all systems continued to perform well. The first Terra post-launch science team meeting was held this past week, with the highlight of the meeting being the display of spectacular images by each of the Terra Instrument Teams. The primary objectives of the meeting were to review the readiness of the spacecraft and instruments to perform the first deep-space calibration maneuver, and to continue coordination for the initial press conference scheduled for April 19th. The review of readiness to perform the deep-space maneuver concluded that the spacecraft and instruments are prepared to proceed with the deep-space maneuver on April 5, 2000. Three of the Terra instruments reiterated their longstanding position that the deep-space maneuver is essential to adequately calibrate their data products. The remaining two instruments realize no significant benefits from the maneuver. Because the maneuver involves intentionally slewing off of the earth, we have asked the GN&C Center to provide an independent review of the planned maneuver, and to participate in the upcoming command authorization meetings (CAM) that proceed the maneuver execution. The GN&C Center Chief has agreed to provide that independent review.

(c) py5aal The first two of a series of attitude maneuvers were successfully completed this week to calibrate the inertial reference units. Six additional attitude slews remain to complete the calibration of the attitude sensors. Plans are also proceeding to perform the first roll maneuver to allow MODIS to perform a lunar calibration using the space-view port on March 24th.

(c) py5aal The first orbit maintenance maneuver was successfully performed this week. This maneuver maintains Terra within a groundtrack tolerance of 20 km.

The planned turn-on of continuous MODIS direct broadcast today, was delayed at the request of NASA Headquarters. Direction is anticipated next week on the approach to be used to fully activate the direct broadcast capability.

The Terra L+90 Party was a great time last night. It was a pleasure to again see many of the folks who were responsible for this great observatory. Special thanks to everyone on the planning team who made the party happen.

Kevin Grady

(c) py5aal Terra is approaching 3 months on-orbit now, and operationally, the daily activities are beginning to settle into a normal mission mode of operati on.

Instrument activities are executed for the most part by onboard ATC loads, with much less ground procedure execution. All systems onboard continue to perform exceptionally and breathtaking imagery is arriving every day.

Plans for the completion of the remaining checkout activities have been finalized. The L+60 Day Review was completed this past week, and in many areas, the performance of the flight systems are exceeding requirements by a significant margin.

Among the subsystems that are performing significantly better than spec requirements, is the TDRSS On-Board Navigation (TONS) System. Terra is flying an autonomous onboard navigation system to provide accurate orbital parameters to the spacecraft in real time. This system represents the first time NASA has flown an onboard navigation as the operational system for orbit solutions. Scientists also receive the TONS output in their data stream.

TONS measures the Doppler data off the forward command signal and processes it in onboard software with a sequential estimation algorithm to produce the real time outputs. The accuracy requirement for TONS is 150 meters in position and 0.16 meters per second in crosstrack velocity, 3 sigma.

(c) py5aal TONS performance has far exceeded the requirement. TONS performance at this time is on the order of 7 meters, one sigma in position and better than 0.015 meters per second in crosstrack velocity. After on-orbit tuning, TONS is expected to provide Terra with onboard position knowledge to better than 5 meters, one sigma and 20 meters, 3 sigma. TONS performance has been monitored during the Terra ascent maneuvers and indicates excellent recovery within the first few measurement updates after the maneuver. TONS filter reconvergence occurs at the beginning of the second post-maneuver contact. TONS also estimates the local oscillator frequency, a drag correction factor, and a TDRS measurement bias for Terra.

(c) py5aal All on-orbit requirements have been exceeded and navigation operations have been performed nominally. TONS data was also used to calibrate the spacecraft clock to aid the operational clock correlation system. The Goddard and Lockheed Navigation Team have done an extraordinary job in developing this navigation subsystem. Congratulations to everyone on the Nav Team. This performance should allow the scientists to geolocate the images even better than expected.

(c) py5aal On a few occasions this past week, problems resulting in solid state recorder buffer overflow, or situations coming close to overflow have occurred. A Team has been formed to characterize the magnitude of the problem, determine the root causes, develop metrics to track performance, and evaluate improvements in the process.

A final reminder to everyone that the Terra Post Launch Party is next Thursday, March 16th. Everyone should purchase their tickets by Monday.

Kevin Grady

(c) py5aal After eleven weeks of on-orbit checkout and verification and a series of orbital ascent maneuvers, the Terra Spacecraft reached its final orbit on February 23. This event was a culmination of years of work for the Terra team with the acquisition Terra's first engineering images. Terra's spacecraft subsystems continue to perform flawlessly, with almost all systems now in their operational science mode. Terra's ground system is providing excellent support for spacecraft command and control, and is performing nominally for the capture and processing of Terra data.

(c) py5aal "We're very excited to see the first engineering images from Terr a," said Dr. Yoram Kaufman, Terra project scientist at NASA Goddard Space Flight Center. "They show that the Terra instruments, with their delicate optics and electronics, made it safely to space. The images give us a glimpse of the unprecedented clarity and richness of the data that we anticipate from Terra in the months and years to come. With these data, Terra starts a revolution in Earth Sciences by observing simultaneously many of the processes in land, ocean and atmosphere that form the Earth System in which we live."

(c) py5aal "Terra's final ascent maneuvers were successfully performed," said Kevin Grady, Terra project manager at NASA's Goddard Space Flight Center, Greenbelt, Md. "Terra is now flying on the World Reference System (WRS), on the same ground track as Landsat 7. Following the initial orbit raising attempt, the Terra team developed a revised plan with eight maneuvers required to raise Terra's orbit. Each maneuver was performed as planned.

"This performance demonstrates the quality and commitment of the entire Terra Operations Team. Everyone involved deservescongratulations for the successful ascent of Terra to its operational orbit," Grady added.

(c) py5aal On February 24, the Moderate-resolution, Imaging Spectroradiometer (MODIS) opened the Earth view door during a pass over eastern North America. The acquisition of science data on board proceeded nominally, and the initial MODIS measurements were successfully downlinked and captured on the ground. The initial image produced by the MODIS Team is a spectacular color image of eastern North America, extending from Canada down through Mexico.

(c) py5aal "A 'first light,' engineering quality, swath of MODIS data over eastern North America reveals that the instrument is working quite well," said Dr. Vince Solomonson, principal investigator for the MODIS instrument.

"These data corroborate that MODIS will provide global, daily,multispectral simultaneous observations of land, ocean, and atmospheric features that will improve substantially our understanding of how the Earth works as asystem.

Unprecedented views of ocean fluorescence, the intensity of fires over land and eruptions of volcanoes, and properties of clouds (e.g, the extent of cirrus clouds) will be forthcoming. MODIS is designed to play a significant role as the Terra mission provides a comprehensive assessment of the state of the planet Earth."

Later that morning, the Multi-angle Imaging SpectroRadiometer (MISR)

(c) py5aal Team opened their instrument cover over central Canada. Again all operations proceeded as planned. Shortly thereafter, the MISR Team produced a spectacular image over Ontario, Canada.

(c) py5aal "These first pictures illustrate many of MISR's new and unique capabilities," said MISR Principal Investigator Dr. David J. Diner of NASA's Jet Propulsion Laboratory. "The instrument, operations system, and science data processing software are performing extremely well and the quality of the images, particularly at the very challenging oblique angles, is outstanding."

(c) py5aal As the week was ending, the Clouds and the Earth's Radiant Energy System (CERES) Team had just completed opening the contamination cover on the CERES aft and fore instrument. Once again, the activation of the cover was nominal. Later in the day, the instruments were configured in the normal mission mode, with one sensor in crosstrack mode, and one in the biaxial mode.

(c) py5aal "Both instruments are on and appear to be working very well," said Dr. Bruce Barkstrom, principal investigator for the CERES Instrument at NASA Langley Research Center. "In normal operation one instrument will scan perpendicular to the Terra ground track, in order to spatially sample the Earth. The other instrument samples the angular distribution of radiation.

(c) py5aal These two Terra instruments join a previous CERES scanner on the Tropical Rainfall Measuring Mission (TRMM), which was launched on November 27,1997. They complement TRMM by extending the observations to cover the globe and by improving sampling of the large diurnal cycle of radiation."

The Advanced spaceborne thermal Emission and Reflection Radiometer (ASTER) completed imaging over Japan on February 24.

(c) py5aal The week of February 27, the Measurements of Pollution in the Troposphere (MOPITT) instrument doors were opened. Later that week, MOPITT's coolers were commanded on and they began collecting science data.

After a little over two months on-orbit, Terra is beginning to produce spectacular imagery. Operationally, Terra will produce 6 terabytes (6 trillion bytes) of data every month, all of which will be available to users for many purposes including science research, applications, and education. The first release of Terra Science imagery is expected for mid-April 2000.

Dave Steitz Allen Kenitze

(c) py5aal Eleven weeks on-orbit now, and Terra continues to perform superbly. The emphasis on the ground has shifted, as expected, to improving our proficiency in handling Terra's science data. All spacecraft subsystems continue to function as expected. The highlight of the week was the activation of the MOPITT instrument. Nadir and space-view doors were opened on Monday, followed by a decontamination period. On Thursday, MOPITT's coolers were turned-on, and the focal planes immediately began cooling down. The detector cooldown was nominal, with the final temperature reached early this morning. Congratulations to the entire MOPITT. Their dedication, perseverance and commitment have always been a special part of the EOS AM development.

(c) py5aal MODIS is continuing to perform detector bias sweeps to characterize and optimize focal plane performance. MODIS continues to cycle between its day and night modes and periodically perform solar calibration checks. MISR is also performing routine day/night cycling, targeted local mode observations, and periodic solar calibrations. CERES is likewise operating in its normal mission mode at this time.

ASTER is in the middle of a two week targeted observation period to complete the functional checkout of the instrument. Observations of Tokyo and the Mayon volcano were completed last weekend. The Team is anxiously awaiting these images which should be spectacular.

(c) py5aal A plan was developed this past week to complete the remaining instrument and attitude sensor calibration slews. The deep-space maneuvers are planned for April. The first orbit maintenance maneuver is likely to move forward to mid-March due to increased solar activity.

(c) py5aal In the past week as we ramped-up the data production, over 7 terabits of data have been downlinked from Terra and captured by the ground system. This is approximately equivalent to seven and a half years of UARS operation or 3 months of Landsat operation. The performance of the Team in capturing the data continues to be good, however we did experience two instances this week in which data was lost. We are continuing to emphasize the importance of dumping the Terra recorder on every TDRSS contact, sothat margin is available when unforeseen events transpire on the ground.

After two and a half months on-orbit, Terra is continuing to perform extremely well. The "L+90 Day" Party has been planned at Goddard for the 16th of March. We hope to see as many of you there as possible. The attached flyer provides more details on the specifics.

Kevin Grady

After years of hard work, our efforts are now beginning to be rewarded with Terra's initial science images. This week we have obtained some spectacular first images. Terra's spacecraft subsystems continue to perform flawlessly, with almost all systems now in their operational science mode.

Terra's final four ascent maneuvers were successfully performed this week.

Terra is now flying on the World Reference System (WRS), on the same ground track as Landsat 7. In total, eight maneuvers were performed, with everyone executed at its planned nominal time. This performance demonstrates the quality and commitment of the entire Terra Operations Team.

Congratulations to everyone involved in the successful ascent of Terra to its operational orbit. We were confronted with an extremely difficult problem, and the Team performed superbly, developing a workaround and new ascent sequence which preserved the option of formation-flying with Landsat 7.

During previous ascent maneuvers the TIR capillary-pumped loop has exhibited a susceptibility to the accelerations induced by the maneuver.

(c) py5aal Following the sixth ascent maneuver, the TIR loop deprimed, an hour and a half after the completion of the maneuver. Thermal engineers believe that the behavior observed in the TIR loop during past maneuvers is due to the fact that the reservoir is oriented differently (than SWIR or MOPITT) with respect to the spacecraft thrust axis. After the fifth burn, the loop retained some small temperature biases, and after the sixth maneuver, the loop finally deprimed. The loop has subsequently been restarted, and the TIR instrument is to be powered-on this afternoon. ASTER has imaging planned for Saturday over Japan. The thermal engineers are evaluating options for making the TIR loop less susceptible to the dynamics of the spacecraft maneuvers.

(c) py5aal On Thursday, MODIS opened the nadir aperture door during a pass over the eastern United States. The acquisition of science data on-board proceeded nominally, and the initial MODIS measurements were successfully downlinked and captured on the ground. The initial image produced by the MODIS Team was a spectacular color image of the Mississippi River delta. One orbit later the MISR Team opened their instrument cover over central Canada. Again all operations proceed as planned. Shortly thereafter, the MISR Team produced a spectacular image of the southern Hudson Bay.

Congratulations to both the MODIS and MISR Teams on their superb performance. This was a milestone we had strived for, for a long time. Congratulations are also in order to the combined efforts of the FOT, EDOS and TDRS Network Team for their superb start in capturing the initial Terra science data. The standard has been set, and the bar is quite high!

As the week was ending, the CERES Team had just completed opening the contamination cover on the aft CERES instrument. Again the activation of the cover was nominal. This afternoon, the contamination cover for the fore CERES will similarly be opened. Later today, the instruments will be configured in the normal mission mode, with one sensor in crosstrack mode, and one in the biaxial mode. Plans are also in place this collect science data this weekend over the Mayon volcano which erupted this week in the Pacific. This will be Terra's first Target of Opportunity.

After a little over two months on-orbit, Terra is beginning to produce the results which many have worked so hard to obtain. If the past week is any indication, the upcoming weeks promise to be very exciting for the Terra community.

Kevin Grady

(c) py5aal The spacecraft power, thermal, GN&C, communications, propulsion, and C&DHsubsystems all continue to perform nominally. Three additional delta-V maneuvers were successfully performed this past week, using the modified thruster pairing matrix. Four maneuvers of a planned series of eight maneuvers have now been completed, with the final eighth maneuver still planned for February 24th. At that point Terra will be in sun-synchronous orbit, flying on the same WRS track as Landsat 7. Two of the remaining four maneuvers will be the first maneuvers of the recent series of eight to be performed during orbit night. This maneuver requires additional spacecraft configuring to minimize the impacts of battery depth of discharge. The first attempt of this orbit night burn will be late this afternoon.

The CERES Team completed diagnostic tests to investigate the encoder anomaly which occurred in the fore instrument. Diagnostic tests did not duplicate the jump observed in the encoder position. It is believed that the root cause of the encoder jump is attributable to a subtle timing issue associated with the azimuth braking operation. The CERES software temporarily disables encoder updates during the braking sequence to avoid erroneous stall monitoring. CERES is very confident the observed encoder drop out anomaly is associated with the braking sequence. The azimuth brake is not applied in normal operations, therefor this feature is presents no threat to the CERES science mission. The fore instrument has been returned to normal cross track scan mode.

(c) py5aal After powering on last week, MODIS transitioned to its A-side science mode this week. The first solar diffuser data collections were performed, blackbody and calibration lamps were functionally checked, the SRCA was functionally checked, and the SMWIR and LWIR focal plane bias sweeps were performed. The bias sweeps were performed to re-optimize the focal plane biases following the resistor changes which were performed prior to launch to reduce crosstalk phenomena that existed in the MODIS data.

(c) py5aal Congratulations are due to the MODIS Team and the checkout they completed this week. MISR used Absolute Time Commands (ATC) to checkout their local mode this past week, as well as normal day/night mode cycling. MISR also power cycled the optical bench heater to examine the camera data sensitivity to the heater controller. MISR is waiting for the final ascent maneuver to open its cover and begin functional checkout of its calibration mechanisms and collection of first images.

(c) py5aal Congratulations to the ASTER Team on generating the first VNIR and a TIR engineering images. The images were spectacular and they provide a glimpse of things to come. A plan to restore SWIR operations has now been agreed to, and that plan begins executing tomorrow. The ASTER Team confirmed that the latch-up condition which occurred in SWIR, only impacts the position telemetry, and that there are no safety related issues. The first SWIR image is planned for February 21st.

A group of flight and ground segment engineers are investigating the time code and packet sequence number bit-flips which have been reported in some of the high rate data. Preliminary statistics indicate that in its worse case, one to two packets out of a million are seeing some kind of bit-flip.

(c) py5aal The majority of the playback sessions (greater than 90%), appear to indicate no bit-flips at all. Presently, the bit-flips are being observed predominantly onMODIS ,althoug that could be an artifact of the present operating modes, and the fact that a limited amount of statistics have been compiled. Tests have been formulated to attempt to isolate where in the high rate data chain the hits could be occurring. Radiation is one potential cause, however the message at this point is extremelyencouraging, in that the error rate of this phenomena is very small. While the number of bit-flips is very small, it has presented a challenge to the ground processing, as the system design is intolerant to such data imperfections. The ground system is presently implementing a manual workaround to deal with these data hits.

After two months on-orbit, Terra continues to operate with all systems nominal. After reaching the sun-synchronous orbit on February 24th, all of the Terra instruments plan on gathering science data on the following day. This past week, the MODIS Team agreed to defer a series of yaw maneuvers that will be used to characterize the solar diffuser to a later date. As a result, CERES, MISR, MODIS and MOPITT will all be opening their nadir covers for the first time on February 25th. This will allow a number of field campaigns that were planned for the late February and early March timeframe to occur as planned, with MODIS and MISR acquiring the necessary data. A special thanks goes to the MODIS Team for accommodating this change. The way things have now fallen into place, February 25th promises to be a memorable date in the history of the Earth Observing System Program.

Kevin Grady

The first of a series of eight delta-V maneuvers was successfully performed this past week, using the modifed thruster pairing matrix. It is this new pairing matrix which accounts for the impingement of thruster plumes on the Terra solar array. The performance of the spacecraft during the maneuver was in excellent agreement with the performance predicted by the simulator.

(c) py5aal Maneuvers will now be performed every other day from now through February 24th, at which point Terra will be in sun-synchronous orbit, flying in formation with Landsat. Congratulations to the entire Team who ran this elusive anomaly to ground.

Science recorder playbacks are now continuing on a routine basis via Ku-band. The solid state recorder replay function has been used successfully since the reallocation of the recorder memory. This reallocation was performed to prevent the replay of science data across data management unit boundaries. A replay across data management units is a suspected cause of the recorder hang-up. We will continue to monitor the replay performance for any reoccurrence of the anomaly observed two weeks ago.

(c) py5aal All three capillary-pumped loops continue to perform as expected. Navigation via the TDRSS On-board Navigation System (TONS) was activated this week. Prior to tuning, the performance is 25 meters, 1 sigma!!! Congratulations to the entire nav Team, some who have worked for the past decade to make this on-board navigation capability a reality. It is an outstanding accomplishment. The CERES Team is continuing their investigation of the anomaly which occurred in the fore instrument. With the azimuth gimbal parked, the encoder position jumped to a different position momentarily, and then returned to the correct position. Physically the gimbal could not have moved this quickly. The first phase of a two phase diagonostic test was performed this week, without a reoccurrence of the encoder jump. Some corruption of the MSByte of the encoder position, is suspected as the underlying cause.

MODIS was powered-on this week, and placed in science mode. The space-view door was opened and and blackbody checkout was in process at weeks end.

After two months on-orbit, Terra continues to operate exceptionally. With all of the high rate instruments now on and generating high rate science data, we will begin stressing the ground system for the first time.

Kevin Grady

Terra continues to perform extremely well as it completes its seventh week on-orbit.

Science data record and playback operations were resumed last weekend. MISR entered their science mode (all 9 cameras on) on Sunday, and began generating high rate science data. ASTER VNIR performed a number of short observations this week, along with a long 16 minute observation. MOPITT and CERES also performed a number of functional checks on their instrume nts this week. Ku-band solid state recorder playbacks are now occurring every orbit, to support the downlink of data generated by CERES, MOPITT, MISR and ASTER. Later in the week, solid state recorder memory allocation assignments for the instruments were updated, to prevent what could be the root cause of the recorder lock-up which was observed last week. It is believed that when the recorder replay function is utilized across data memory unit boundaries, there is a potential for locking-up the recorder. The memory reassignments will prevent this type of replay from occurring. Some problems have been encountered in the science data downlink process, but overall we are pleased with the initial successes. There is certainly room for improving our proficiency, and that will come in time as we continue the Terra activation.

After three weeks of data analysis, simulations and engineering thruster firings, the root cause of the anomalous attitude transients during the first of the long delta-V maneuvers is now understood. For some time we have believed that at least three contributing factors would be necessary to account for the observed behavior. Two have been known, but the third eluded the Team until we completed last weeks thruster firings. This past Tuesday, thruster plume impingement analyses were completed, and the analyses confirmed that large disturbances could be produced by interacting with the solar array. As it turned-out, the orbit position in which Terra performed the first large delta-V maneuver, was the orbital position which produced the maximum amount of roll torque. This explained the sluggish behavior of the roll control during the maneuver.

The torques generated by the plume impingement of two attitude thrusters were incorporated into the Terra attitude simulation, and the simulator replicated the behavior of the aborted burn. On Wednesday, two short delta-V maneuvers were performed, with more optimal solar array orientation. The burns were successful, and the response of the spacecraft was predicted again by the simulator. To account for the extraneous torques which are produced by the plumes, a modification will be made to the thruster pairing matrix. This is the on-board logic which determines which thrusters will be fired, when a specific torque is desired. Thus, the additional external disturbances which are produced by the plume, will be factored into the fire control signals. A burn sequence has now been developed which starts on February 10th, and ends on February 24th, placing Terra in the same orbit and WRS ground track as Landsat 7.

This has been a difficult anomaly to run to ground, because of the multiple contributing factors. The engineers involved in this anomaly closure have done an incredible job in getting to the bottom of this issue. A special thanks to everyone who participated in this investigation and resolution, it was truly an excellent piece of work.

The TIR capillary-pumped loop has continued to perform well, and all indications are that the deprime phenomena has been resolved. Stability has now been demonstrated, and the TIR instrument has been turned back-on.

Our seventh week on-orbit has been quite successful, and we look forward to achieving our final orbit and obtaining the first instrument observations.

Kevin Grady

The analysis of the possible moment arm effects due to control thruster plume impingement on a canted solar array for roll contributions was completed. The effect is not negligible and when factored into the updated spacecraft ascent maneuver dynamics model, completely and accurately accounts for the observed behavior of the initial ascent maneuver abort. The plume impingement effect is the final contributor added to the ascent maneuver anomaly puzzle. Plans are proceeding to conducted back to back 20 sec burns in a single contact tomorrow. There will be sufficient separation between the burns to verify and confirm effective and proper control of spacecraft attitude before the second burn is attempted. We are eagerly looking forward to favorable results. If the behavior is well conditioned we may be able to perserve the goal of being on orbit by Feb 13. We still have to wait and see tomorrow's results.

On the instrument front, MOPITT completed all the setup tasks to configure for the pressure modulated cell characterizations over the next three days. MOPITT is now in science mode and all mechanism performance is nominal.

CERES was removed from safe mode to resume the series of ATC mode sequence checkouts. CERES will also intersperse a couple of orbits of real time azimuth scan checks over the next few days.

MISR is still in global mode generating "dark" detector output. MISR has indicated after a few startup problems that MISR science data is reliably flowing to the SCF.

ASTER completed the initial VNIR and SWIR observation functional checks. The VNIR calibration photodiode checks of the primary and backup lamps were also completed. During the second SWIR observation functional checkout event the SWIR pointing mirror telemetry latched up. This problem has been observed in previous I&T testing, although not under the same circumstances. SWIR operations are on hold while the ASTER engineers assess the situation and develop the necessary diagnosis and recovery plan. This problem is normal handled by a power reset of the SWIR power supplies, however, the specific conditions at the time of the fault are being reviewed to determine if this is still the proper course of action. We expect some feedback from Japan tomorrow.

Tom Anderson

ASTER TIR Reconfigured from Safe Mode to TIR Cooldown Mode-Cooler Cooldown Profile Nominal

-CPHTS Thermal Regulation Remains Tight and Unchangedv

ASTER VNIR and SWIR Calibration Checks via ATC Commanding Functionally Successful

CERES Fore and Aft Units Reconfigured from Safe to Standby to Reactivate ATC Stored Command Timelines

Current Configuration:

-ASTER SWIR in Operational Mode; VNIR in Operational mode, TIR in Cooldown Mode

Last week I suggested that this week might be a challenging andinvigorating week for the Terra Operations Team. I did not expect it to be asinvigorating as 20 inches of snow. While most of Goddard relaxed on atwo-day vacation with the closure of the Center, operations in the TerraControl Center in building 32, continued on, at the usual exhausting pace.

It is fortunate that even this most recent blizzard did not impede theresolve of this Team, as a number of challenging issues were brought toclosure during these past few days. The commitment of individuals on this Team remains phenomenal.

The week began with MODIS opening their space view door and configuring into science mode. These activities allow the passive radiator to view cold space and also begin the generation of high rate data. Both of these activities completed as planned, and MODIS began to warm up gradually at the higher level of dissipation. The first recorder dump of MODIS science data executed as planned, and the data was routed to the DAAC and the MODIS Science Team for analysis. The nadir aperture door on MODIS is still closed, and it will remain in that state until the first image is taken in February.

In the middle of the blizzard, ASTER also took the opportunity to perform VNIR and SWIR pointing checks. Both of these movements were successful.

The performance of the capillary-pumped loop on TIR is now looking outstanding. After analyzing the data from the two de-prime anomalies, the thermal engineers have concluded that there were two issues causing the instabilities that were observed in the TIR loop. Both have now been corrected. The de-prime of the loop, appears to be caused by the formation of vapor bubbles at loop start-up. A large inrush of liquid into the reservoir,appears to be creating the vapor bubbles. This inrush and bubble generation was reduced by using a start-up scenario which results in a more gradual turn-on of the loop, reducing the inrush of liquid into the reservoir. The second unexpected behavior which was observed last weekend after the loop was restarted, were small oscillations of the reservoir set point temperature. It is believed that the variations are caused by the fact that a vapor/liquid transition boundary is falling at the physical point in which the control thermistor is located. When control was switched to a different control thermistor, the oscillations disappeared. The TIR loop is now duplicating the behavior of the MOPITT and ASTER SWIR loops, both which have been solid. The loop will be monitored over the next several days, with turn-on of TIR possibly as early as Monday. These two-phase thermal control loops are state-of-the-art hardware, that have virtually no long-term spacecraft applications history. The Terra thermal engineers need to be acknowledged for the superb job they have performed in running this anomaly to ground, as well as the outstanding performance of the CPHTS hardware to date.

The anomaly which has been of interest to most people is the issue of the orbit ascent maneuvers. During the attempt of the first long ascent maneuver, Terra's flight computer detected a roll attitude anomaly, and properly aborted the maneuver approximately one minute into the burn. The data has now been analyzed and a strategy mapped-out for completing an ascent sequence. Three items have been identified as potential contributing factors to the anomalous behavior. Four firings will take place over the next week to prepare for the ascent sequence, and eliminate (or establish) anomalous thruster performance as one of the contributing factors. The first two firings are planned for today, and the final two next Tuesday and Wednesday. During the blizzard on Tuesday, the Lockheed Valley Forge Team presented the results of their data review and analyses of the aborted maneuver. The quality and depth of the investigation were outstanding, particularly in light of the fact that operations and activation had to continue, along with other issues being worked. The Team performed an outstanding job, on a problem that has been elusive to pin down. The bottom line of all of this, is that we now have a plan, of performing a series of burns, which will place Terra in the operational orbit, in formation with Landsat 7. It is a challenging plan, and the possibility does exist that we will learn something in the engineering burns which will force a reconsideration of the plan. We will always proceed with safety first and foremost when the maneuvering of Terra is planned.

Just as the blizzard started on Tuesday morning, we were confronted with our latest anomaly on Terra. During a routine housekeeping recorder playback, the solid state recorder playback hung-up. This housekeeping playback operation followed a successful MODIS science playback and replay on the previous orbit. The MODIS replay was unusual in that it transitioned between the recorders two mass memory units twice during the replay. It is not known if this was the cause, but it is very similar to the recorder playback hang, which occurred during the second end-to-end test prior to launch. However it is not identical, since it was a science playback following a multi-buffer replay in the previous ground anomaly.

Regardless, replays across memory unit boundaries with not occur in the future. This will have no impact on science data record or playback. A number of diagnostics were run on the recorder in the hung state, and finally the recorder was reset to clear the anomaly. Housekeeping record and playback began working nominally. Science record will take another day or two to complete the modification and test of a memory patch procedure which needs to be performed prior to initiating science data record.

Science data record should be operational tomorrow. The solid state recorder manufacturer is in the process of reviewing the diagnostic dumps, to determine the root cause of the playback hang. At that point, we will determine if addition replay constraints are warranted.

High gain antenna radiation hits have begun reoccurring eriodically, however we are now seeing them on the descending passes through the South Atlantic Anomaly. The telemetry monitor continues to successfully restart the antenna after each of these events. The change from ascending to descending direction is likely explained by the fact that the orbit hasprecessed sufficiently such that the descending passes through the "duck" are now at higher altitudes. Flight dynamics engineers are in the process of confirming this theory. If correct, it does demonstrate the strong dependence of proton density with altitude.

Our sixth week on-orbit will certainly go down as a memorable one. I remain extremely pleased with the ability of the Team to confront new challenges and rapidly resolve them, always maintaining a disciplined attitude toward mission safety.

Kevin Grady

Today will go down as a day which we all will hope to soon forget. It was one of those days that certainly did not go as we had hoped. Four opportunities were planned to execute two sets of one second thruster firings. At the end of the day, we were forced to wave-off on three of the four attempts, with the fourth attempt partially successful, however with an unplanned early termination. The first wave-off was caused by a misconfiguration of the comm link. The last wave-off was caused by the fact that we had a failure in one of the command lines to White Sands, and therefor had no back-up line. In both of the instances, the prudent thing to do was to wave-off, as we were not going to proceed with a test such as a thruster firing, with anything less than 100% of our communications capability available. The second wave-off occurred after we fired the fifth of eight one second thruster firings. An attitude rate threshold which was designed for the normal quiescent science mode was exceeded when the fifth thruster firing occurred. The threshold was exceeded by 0.01 deg/sec, with the result being that attitude control transferred over to the independent ACE A safehold processor. The threshold should have been increased from 0.02 deg/sec to 0.09 deg/sec, to account for the rates which would be induced by the 1 second thruster firings. Thus, attitude and rate errors during the shutdown were extremely small. Control was re-established back under normal SCC control in less than three hours. The third wave-off was necessary to recover from rate limit trip, and to plan for the fourth attempt, which was subsequently scrubbed due to the lack of a redundant command line on the ground. All in all, we accomplished only a fraction of what we set out to complete, while we expended significantly more effort. Completion of the partially completed thruster firing is planned for tomorrow. The second set of one second thruster firings will be deferred for now, and we will proceed with the 20 second delta-V burn on Tuesday.

With almost five weeks on-orbit now, Terra continues to perform extremelywell. The instruments outgassing process continues while the spacecraftflies in the normal mission control mode, under the control of thespacecraftcontrols computer. Normal high gain antenna operation continues for forward and return link communications, with the exception that Ku band dumps have been less frequent, with the high rate instruments not yet in their science modes. This will change next week, with the turn-on of ASTER, MISR and MODIS, at which point Ku band solid state recorder dumps will occur each orbit. The end-to-end proficiency of the Ku-band dumps still needs to improve, however overall we are about were we expected to be, anticipating that in would take a number of weeks to hone the operation.

X-band recorder dumps to the EPGN are also being scheduled periodically, to improve and retain the proficiency of that capability. The X-band direct broadcast capability was also checked for the first time this week. The antenna on Building 23 at GSFC tracked the spacecraft and examined the quality of the signal received. A receiver is expected to be returned shortly which will enable the Building 23 ground station to strip-out the data which is being transmitted. There was one additional high gain antenna reset in the "duck" region of the South Atlantic Anomaly this week.

The telemetry monitor in the flight computer, reset the electronics and TDRSS tracking resumed as planned.

As the week ends, CERES had both instruments powered-on and in the crosstrack mode, MODIS was in standby mode with passive cooler outgassing completed, and MOPITT remained in safe mode. ASTER SWIR was also in safe mode, VNIR and TIR in survival mode, and MISR remained in its outgassing mode. CERES took advantage of the past week to perform a number of activation and check-out tests. CERES sun-avoidance logic, elevation and azimuth angle motion, science data sensitivity to azimuth motion, spacecraft disturbance induced by CERES azimuth motion, checkout of internal calibration and solar calibration modes, were all successfully checked. Congratulations to the CERES team on an extremely successful week. MODIS, MISR and ASTER SWIR and VNIR also plan on initiating their science modes next week. Covers will still remain closed on MODIS and MISR, however the spacecraft will record the high rate data stream, with recorder dumps each orbit. It promises to be a challenging and excitingweek for the three instruments.

Anomaly investigations remain focused on the delta-V problem experienced on January 11th, and the de-prime anomaly observed on the TIR capillary-pumped loop. The root cause of the anomalous spacecraft motion during the maneuver on January 11th is still not known, however at least one contributing factor has now been identified. GN&C engineers are meeting all day today to review the data analyses performed to date, and develop a plan on how we will proceed. The question at this point is what path we will have to take to execute the remaining orbit maneuver. One end of the spectrum has us changing the spacecraft configuration and initiating the series of maneuvers as early as January 31st. The other end of the spectrum could be a software change which would take longer, due to the rigor which must be imposed to validate the changes. Regardless of the scenario, there is no question of Terra getting to the sun-snyc orbit, just a question of when.

The other anomaly being worked is the de-prime of the capillary-pumped loop for ASTER TIR. The second attempt at running the loop produced results very similar to the shutdown which occurred the first time. The loop has been restarted using the contingency start-up procedure. The loop is presently running, however the performance is slightly warmer than expected. The backup reservoir has been set lower than the prime to decrease the likelihood of de-prime. The thermal engineers are also engaged in a data review today, to determine the next course of action should the loop de-prime.

During this past week, an ATC load was up linked which over wrote the stored command portion of commands which were to be issued at the end of the previous days load. This resulted in the spacecraft not being correctly configured for a TDRS contact. A negative acquisition procedure was executed which configured the spacecraft to the omni antenna. There was no spacecraft safety issue, only the loss of ten minutes of real-time contact due to the error. An Anomaly Review Team was formed to investigate the exact cause of the problem and to make recommendations to prevent another such occurrence.

Overall I remain extremely pleased with the performance of the team and spacecraft. We are now very close to the collection of science data, at the magnitude in which we have designed both the flight and ground segments.

Next week promises to be a challenging and invigorating week.

Kevin Grady

With Terra on-orbit for almost four weeks now, both the spacecraft and instruments continue to perform extremely well. Instruments are continuing their outgas period. The spacecraft is presently flying under the control of the spacecraft controls computer, with the high gain antenna being used for both S and Ku band dumps. X-band dumps are also being scheduled periodically, with preliminary indications that the first X-band contact which was recorded last week, contained good recoverable data.

Earlier in the week, the high gain antenna motor drive electronic breadboard testing at EMS (Spar) was completed. The breadboard and additional piece part testing confirmed that there are no overstress issues as a result of the sensitivity of the optocouplers to proton radiation.

GSFC parts and electronics engineers who performed similar piece part testing, concurred with the conclusions of EMS. There are now no operational constraints on the use of the high gain antenna through the South Atlantic Anomaly. The telemetry monitor to reset the motor drive electronics remains activated.

On Monday, Terra attempted and completed its first delta-V maneuver. This was a short 11 second burn to establish the functionality of the thruster attitude control and translation control modes.

At the time, we believed we had validated the orbit adjust control capability of Terra. The following day, we were attempting the first of four large maneuvers, when the flight computer aborted the maneuver 66 seconds into the burn. The flight software shutdown the maneuver, 66.5 seconds into a planned 8.5 minute burn, when the spacecraft rolled 4 degrees off the earth.

The roll angle continued to grow, and after exceeding a second threshold, the spacecraft's control computer correctly handed attitude control over to the safehold processor. The safehold controller immediately reduced the roll error to zero.

The spacecraft was safe at all time, and no telemetry was data lost. The Team is in the process of analyzing the telemetry and developing a new burn sequence to get Terra to its final orbit at the earliest possible date, with no compromise to mission safety.

At the moment, the controls engineers are converging on the root cause, and we expect to have isolated it by the end of the weekend.

On Monday we will be able to construct a new plan which incorporates time to correct the underlying problem, perform another engineering burn, and establish a burn sequence which allows us to formation fly with Landsat 7.

This week also resulted in the completion of the initial turn-on of the three ASTER sensors, VNIR, SWIR and TIR.

All was proceeding well, with both ASTER capillary-pumped loops running, until an anomaly occurred on early Monday morning.

Early Monday, it was observed that line temperatures in the TIR loop, were beginning to rise, indicating that the capillary-pumped loop was beginning to de-prime.

TIR was powered down, and remains in that state. Thermal engineers now believe that the root cause was a vapor bubble which was created at start-up of the loop.

This likely is the result of the long cold soak which occurred in the early part of the mission.

The TIR capillary-pumped loop is now running, using the coldplate heaters as the load. TIR will be powered-on next week, after the performance of the loop has been monitored for several days. The loop is running rock solid at this time.

The packaging and shipment of the last of the Terra ground support equipment was also completed this week at Vandenberg.

Most of the equipment returns to Valley Forge for final dispositioning, and some of the equipment was shipped directly back to Goddard.

Again I would like to thank the I&T Team who performed such an extraordinary job over the past few years, and particularly last year at the launch site.

Their dedication and sacrifice has given the earth science community the extraordinary opportunity to study the planet in a manner which promises to have profound impacts on mankind's understanding of our home. Thanks to everyone who hung in there.

Kevin Grady

ASTER TIR Cool Down

Command: AST_TIR_COOL_DOWN

PROC Completed at GMT 14:40:50

COOL DOWN TIME 22M57S

The temperature of TIR Detector has successfully gone down to 80.649K.

Monitoring will be continued.

TMON 43,44Enable

Command: FS1_EXEC_TMON_GRP_PROC(1,43,44)

Mirror Rotation is scheduled

Time: 13:32:32 on January 11th GMT, approximately 23 hoursafter the ASTER

TIR Cool Down.

We, ASTER GDS, will stay here to witness the Mirror Rotation and will then leave for home tonight. It is decided not to conduct the temperature setting of VNIR Telescope on 1/11 due to the current stability of the temperature.

Engineering Maneuver scheduled tonight.

Time: January 10th 17:55:42.150 GMT

(January 11th 1:55:42.150 JST)

Outcomes

1) SWIR/TIR CPHTS is now operating in normal fashion. (The temperature of Cold Plate=20.1-22.5 degrees centigrade.)

2) Power-on of MPS/CSP/VNIR was successfully performed. Normal operation was confirmed by each Sub-System. Command and Telemetry are all working well. SWIR is now switched to Observation Mode and now under normal operation.

3) Cool Down of SWIR/TIR was successfully performed. It took 22m6s for SWIR and 22m57s for TIR (Ground test was approximately 23 minutes). The eventual temperature was 76.98K for SWIR and 80.65K for TIR.

4) All the 4 launch locks were successfully released by the first command transmission.

5) TMON#41-#45 were loaded in the Flight S/W and were enabled.

Events planned for the next week

1) TIR Mirror Rotation

Note: "VNIR Temp. Set", which was going to take place next week, is no longer required since the temperature of VNIR Telescope varies in a stable range from 21.5-22.5 degrees centigrade on the orbit.

January 7 , 2000----ASTER GDS

All the activation events which started in the Contact Session on January 7th at 14:21 GMT (23:21JST) were all successful.The followings are the commands transmitted:

(ASTER SWIR LLOCK1 OFF/TIR CLL1 OFF)

AST_TIR_CLL1_OFF

(ASTER MPS TURN ON)

AST_MPS_ON

(ASTER TIR SCAN LLOCK OFF)

AST_TIR_SCAN_LLK1_OFF

(ASTER CSP&VNIR POWER ON)

AST_CSP_A_ON

AST_VNIR_A_ON

(ASTER VNIR LLOCK OFF)

AST_VNIR_LLOCK_A_OFF

(ASTER OPERATIONAL POWER ON)

AST_SWIR_COOL_DOWN

AST_SWIR_OBS_SET

The last command was completed at 23:28:35GMT (on January 8th at 23:28:35JST).

All the Launch locks of ASTER related equipment are now released. ASTER major events coming up next will be related to TIR, which are scheduled on January 9th evening to January 10th morning JST.

Activation of the Terra spacecraft is continuing at a brisk pace. At weeks beginning, the spacecraft was placed back in the normal control mode (hadbeen in earth sensor based acquisition mode during Y2K rollover), with communications via the high gain antenna. MOPITT and MODIS were powered-on , joining CERES and MISR which were powered-on before the New Year. All three MODIS door latches were released: nadir aperture, space view and solar diffuser. MODIS remains in the outgas mode, with doors closed, and launch latches released. MOPITT was powered-on and its standby mode was checked. In addition, MISR has now powered-on its nine cameras, and also has its outgas heaters on.

The second of the three capillary pumped loops was activated this week.

The MOPITT and ASTER SWIR capillary pumped loops are now operating. The last of the three loops will be started in the next few days, prior to ASTER TIR turn-on.

The X-band and Ku-band science data links were also checked this week.

The X-band link was checked using a pseudo-random bit stream (PRBS) and a short housekeeping playback. The data was recorded on tape and is in the process of being shipped to GSFC for processing. Electronic transmission of the science data from the X-band sites to Goddard, is not planned until the spring of this year. This capability is being developed to support the PM mission. Terra science data will be recorded on tape, and shipped to GSFC, for all X-band dumps over the next four months. The spacecraft's Ku-band link was also successfully checked using PRBS, with excellent bit error rate performance.

The first of several planned attitude sensor calibration slews was successfully performed. Initial data indicates that the spacecraft jitter induced by the high gain antenna is significantly reduced by the feedforward capability. The earth sensors and the star trackers continue to be reliable detectors of the South Atlantic Anomaly. Neither of these features should effect attitude performance.

The converter load prior to the test had been the expected value, and it should have returned to this original value at the completion of the test.

All of the propulsion system attitude and translation thrusters have now been successfully test fired. At the completion of the thruster test on Tuesday, it was noted that the power being drawn by the propulsion system power converter, was slightly less than the value at the start of the test.

Subsequent analysis and troubleshooting have determined that one of the four resistive load circuits that are on the output of the converter to maintain stability, appear to have gone open circuit. The observed reduction in current was equal to the load expected for each of the load circuits.

Subsequent troubleshooting identified which of the four circuits had opened.

Historical thermal/vacuum data was reviewed, and preliminary indications are that power supply stability would not be an issue with the 25% reduction in the load box dissipation. However, as a conservative measure, we are turning-on an additional load in the propulsion system to maintain the converter load in the specified range in which stability is guaranteed.

On Wednesday we were informed by the high gain antenna developer, that additional analysis and breadboard testing should be performed, before we could be guaranteed that the transients induced in the South Atlantic Anomaly, were not stressing parts in the motor drive actuator (MDA) electronics. GSFC parts engineers were consulted, and they agreed with the conservative course of shutting power off to the MDA during the SAA, until the analyses and breadboard tests were completed. Within a couple hours, the launch activation team had identified a software patch and a telemetry monitor to remove power from the MDA during passes through the SAA.

While the software patches are being written and tested, the operational mode will be to park the high gain antenna, rather than manually start and stop it eight or more times a day. The robustness the TDRSS omni link allows us to get 16 kbps housekeeping data even without the high gain, so the simpler interim operational mode was selected. Again it is a credit to the Operations Team that they can respond with a solution to a difficult challenge so rapidly, and keep the activation interruptions to a minimum. We also need to acknowledge the fact that a number of our Team members are back at Vandenberg, packing all of the ground support equipment which we brought out to California last April. This launch campaign was certainly longer than anyone ever expected, and the it was our I&T Team that was on the short end of the stick while the launch vehicle situation was sorted-out.

A special thanks to the Terra Integration and Test Team, for the superb job they did in getting our spacecraft ready for launch. The performance of Terra over the last three weeks is the ultimate testimony to the thoroughness and dedication which our I&T Team brought to the job.

You will not find a more capable I&T group anywhere.

Kevin Grady

As you all probably know by now, Terra spacecraft with optical sensorASTER installed was successfully launched on Launch Vehcle Atlass II from Vandenberg Air Force Base in California, USA, at 10:57:40.819am on December 18th PST(3:57:40.819am on December 19th JST), 1999.

Approximately 14 minutes later, Spacecraft Separation also succeeded followed by smooth deploys of Solar Array and High Gain Antenna. Terra is now travelling in an orbit slightly lower than its final orbit and it will repeat Acsent Burn until it acquires the planned orbit.

The spacecraft was formerly called EOS-AM1 and was renamed Terra last year as a result of public collection. ASTER, a name of a flower which is a kind of chrysanthemum, is now to bloom on Terra(meaning the earth, the ground.)

At the beginning of Y2K, ASTER will have its Launch Lock off early January, then will go through the instrument checks followed by the very first transfer of the target observation data.

We, ASTER GDS, are prepared to proceed checking on this initial image data in cooperation with the ASTER Science Team. We will be ready to deliver the ASTER data after the Initial Checkout ends.

I would very much appreciate it if you could utilize our ASTER data after the completion of the Initial Checkout while we will keep on providing the updates of this Home Page when necessary.

Hiroshi Watanabe

ASTER GDS Project Manager

(c) py5aal With the launch near at hand, both the NASA side and the Japanese side are making final adjustments. Terra has the same orbit as LANDSAT 7 which is already in orbit, successfully transmitting data to the ground. ASTER GDS is looking forward to receiving ASTER data very soon. ASTER GDS is scheduled to have an Initial Checkout Time which will last for about four months after the launch. And afterwards, a real opening to the public is scheduled. From now until then, an introductory home page on the function of the ASTER GDS is opened to the public, so please enjoy your trip through this web site. We hope it will be informative and interesting to you.