ROSAT Re-entry

ROSAT (short for ntgensatellit, in German X-rays are called Röntgenstrahlen, in honour of Wilhelm Röntgen) is a defunct German Aerospace Center-led satellite X-ray telescope, with instruments built by Germany, the UK and the US. It was launched on 1 June 1990, on a Delta II rocket from Cape Canaveral, on what was initially designed as an 18 month mission, with provision for up to 5 years of operation. ROSAT actually operated for over 8 years, finally shutting down on 12 February 1999.

ROSAT is expected to re-enter the Earth's atmosphere between October 21 and 23 2011. In February 2011, it was reported that the 2,400 kg satellite was unlikely to burn up entirely while re-entering the earth atmosphere due to the large amount of ceramics and glass used in construction. Parts as heavy as 400 kg could impact the surface intact.[1]

(from Wikipedia)

Links


"Live" Stats

These sites do on demand calculations of satellite position based on an observer's location and recent satellite elements (via NORAD).

Guide to viewing ROSAT in Orbit

Before re-entry, as with other satellites, ROSAT will be visible from occasionally depending on your location, satellite position and time of day.  A satellite is potentially visible when it is lit by the sun, and is bright enough to be seen against the sky (the darker the sky the better).  There is only a small window (near the satellite's orbital sunrise and orbital sunset) when it will be both lit by the sun and visible to an observer with a dark enough sky.  Stand-alone and online software can assist in predicting visible passes of a satellite for your location.

The world map based visibility guide (see below) allows you to quickly get an estimate on whether you are near enough to be able to sight a visual pass. 

Re-Entry

Predictions

Who does this?
Data and Simulation

Current Estimation

These estimates and ranges very.

Current Projection & Prediction UTC (as at 21.8-Oct)

 aero.org  23 OCT 13:24 UTC  ± 16h  @20.8-Oct
 Space-Track.org  23 OCT 05:49 UTC  ± 24h  @21.2-Oct
 Ted Molczan  23 OCT 11:30 UTC  ± 12h  @21.0-Oct
 Harro Zimmer  23 OCT 07:21 UTC  ±  6h  @20.7-Oct
 TS Kelso  23 OCT 02:47 UTC  ±  ?h  @20.7-Oct
 @ROSAT_Reentry  23 OCT 11:00 UTC  ±  9h*  @19.5-Oct

The atmospheric density and thus the re-entry times are heavily effected by Solar Flux, which has been predicted to rise above nominal levels in the coming week.  This will lead to a decay earlier than expected by possibly a day or two.

Count-down clock app (iPhone)

NOTAM

FAA issues NOTAM:
!FDC 1/9172 FDC .. SPECIAL NOTICE .. EFFECTIVE IMMEDIATELY UNTIL 1110252359 UTC. AIRCRAFT ARE ADVISED THAT A POTENTIAL HAZARD MAY OCCUR DUE TO REENTRY OF THE SATELLITE ROSAT INTO THE EARTH'S ATMOSPHERE. THE FEDERAL AVIATION ADMINISTRATION (FAA) IS WORKING WITH THE DEPARTMENT OF DEFENSE (DOD) AND THE NATIONAL AERONAUTICS AND SPACE ADMINISTRATION (NASA) TO ENSURE THAT THE MOST CURRENT RE-ENTRY INFORMATION IS PROVIDED TO OPERATORS AS QUICKLY AS POSSIBLE. FURTHER NOTAMS WILL BE ISSUED IF SPECIFIC INFORMATION BECOMES AVAILABLE INDICATING A UNITED STATES (US) AIRSPACE IMPACT. IN THE INTEREST OF FLIGHT SAFETY, IT IS CRITICAL THAT ALL PILOTS/FLIGHT CREW MEMBERS REPORT ANY OBSERVED FALLING SPACE DEBRIS TO THE APPROPRIATE ATC FACILITY AND INCLUDE POSITION, ALTITUDE, TIME, AND DIRECTION OF DEBRIS OBSERVED. THE DOMESTIC EVENTS NETWORK /DEN/ TELEPHONE 202-493-5107, IS THE FAA COORDINATION FACILITY. 

Re-entry Experience

Once the ROSAT reaches the height of 120 km (75 miles) above the Earth's surface it will have only around 30 minutes left before re-entry (less than one third of an orbit).  Re-entry is generally accepted as commencing from orbit around at around 80km altitude.  At this point the acceleration due to drag becomes appreciable (greater than 0.1G) thus causing further irreversible loss of altitude and increase in drag.  At peak deceleration extreme heating, due to friction, and drag forces can destroy the objects integrity and disintegrate part or all of the object. This continues to around 45km altitude when the remaining objects have slowed and deceleration forces decrease.  Remaining objects continue a ballistic trajectory, impacting the earths surface.

Twitter

Visual Observations


Recent Graphs

The decay graph is a simple plot of observed perigee and apogee, plus a few days more of "calculated" perigee and apogees, superimposed with a numerical simulation of an object re-entering a standard atmosphere.  The co-efficient of drag is adjusted to allow the graphs to follow closely for previous observed values, and then effectively extrapolated to the eventual re-entry of the object.

The visual map (see above), is a guide to help identify global location that may get a visual on the orbiting satellite.

The track map shows an indicative path over which the decaying satellite travels as predicted around re-entry time.

decay

ROSAT Projection 22 v2

visual

ROSAT world visibility 2011-10-22

track


ROSAT Re-entry Tracks 2011-10-20

files

At the end of the page is a Google Earth kml file that can be File->Opened to show the orbital tracks.  Will try to update these with date/time stamps.  This kml file may/will change as more updates are applied.

  • The file rosat.kml is path only (and ground path).
  • A simple addition of time stamps on the location has been added for the file rosat-points.kml
  • File rosat-vis.kml has (shortened) timestamps, yellow path for a Lit satellite (by the sun), cyan path for unlit, and a green stripe for the center path of a visible path (where sky is nautical twilight or darker).
  • An quick rosat-vis+live.kml experiment adding an AGI provided live location and combining with the above file.
  • Using @ROSAT_Reentry orbit data directly rosat-vis+live-ftest.kml 
  • Post analysis re-entry range rosat-reentry.kml
  • Post analysis 3 hours prior to re-entry range rosat-prior-3h.kml


Google Earth ROSAT 1

rosat-vis.kml sample file


Glossary

  • Apogee : Furthest from Earth (within a particular orbit)
  • Elements
  • NORAD
  • Perigee : Closest approach to Earth (within a particular orbit)
  • TIP
  • TLE
[Last Updated 2011-10-16 02:45GMT]

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live.kml
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Paul Salanitri,
Oct 28, 2011, 1:45 PM
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rosat-points.kml
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Paul Salanitri,
Oct 21, 2011, 9:18 PM
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rosat-prior-3h.kml
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Paul Salanitri,
Oct 23, 2011, 7:06 AM
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rosat-reentry.kml
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Paul Salanitri,
Oct 23, 2011, 7:07 AM
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rosat-vis+live-ftest.kml
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Paul Salanitri,
Oct 22, 2011, 3:01 PM
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rosat-vis+live.kml
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Paul Salanitri,
Oct 22, 2011, 2:59 PM
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rosat-vis.kml
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Paul Salanitri,
Oct 22, 2011, 4:01 AM
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rosat.kml
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Paul Salanitri,
Oct 21, 2011, 7:56 PM