1.UNITEC-1 On-board TransmitterTable. Specification of UNITEC-1 on-board transmitter
2.Data FormatModulation of 96% of the downlink data is CW with 1bps. Transceiver switching ON/OFF makes signals 1/0. A statement (switching on or off) keeps 1 second.Only 4% of the total data is 1200 bps AFSK/FM. Basic concept of UNITEC-1 data modulation design is using the 1bps CW to increase a reception power ratio. 2.1 Downlink CycleA task sequence for UNITEC-1 OBC is defined as a “major cycle”. It keeps 6 hours. Major cycle sequence is written in a Table 3. Data is transmitted in periods which is shown as 【Downlink】. UOBC (University On-Board Computer) is tested in a statement of “UOBC experiment”. Main OBC (MOBC) communicates with each UOBC and tests them. A result is sent as a experiment data to ground stations. Table. Major Cycle (6 hours) Content
(*)Orbital determination downlink“1”s are sent 120 times, which keeps. It means constant signal is transmitted during 120 seconds. This can be used to acquire parameters such as satellite position and Doppler frequency to determine the UNITEC-1 orbit. (**)Major downlinkMajor downlink includes a housekeeping data and science data. Each UOBC has individual data packet window which modulation is AFSK/FM. (***)Minor downlinkMinor downlink includes a housekeeping data and science data. UOBC results aren’t included and AFSK/FM communication isn’t operated. Table 4 shows a sequence of the minor downlink. 2.2 Major & Minor Downlink Data FormatPlease read this document for the details.2.3 UOBC Downlink Data FormatPlease read this document for the details. |
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Downlink Specification |