Sunsat status 1 July 1999

  Item   Feature Status ( on 1 July 1999 unless indicated in Date column) Date
  Thermal   Summary OK.  
      Comment Battery temp sometimes high. See battery comments.  
      Internal OK Typically + 22 C.  
      Battery temp OK but a bit high --- typically + 20 C  
      Solar panels OK varying from - 30 C. to + 68 C. Highest when no spin = + 110 C.  
  Power   Summary OK.  
      Comment Power margin low in 12h00 orbit. See Power Margin  
      Battery condition Good. No known problem  
      Voltage Varying from 14 V (Charge) to 12.5 V (Discharge)  
      Charge termination Working well based on battery voltage  
      Charging control Working well  
      SOC meter State Of Charge meter is working well. Shows SOC dropping from 100% to 60% after long high current operations  
      Power margin SOC increases by 2% = 0.12AH per orbit when OBC1 and RAM disk operating on 28 June 99. This near 12h00 orbit is minimum power. Can be increased by raising yaw rate to induce more roll bias  
  Telecommand   Summary OK.  
      Hardware telecommand Working well with no known false commands having occurred  
      Diary commands Working well after OBC1 update 1.  
  Telemetry   Summary OK.  
      Real time TLM Good. 1200 bd modulation serves as good beacon.  
      WOD Whole Orbit Data collection is working well.  
  Uplinks   Summary OK  
      VHF Working well from a few degrees above horizon. Sensitivity not yet quantified since ground station uses maximum capability of 25 watts and 12 dBi antennas  
      UHF Working well from a few degrees above horizon. Sensitivity not yet quantified since ground station uses maximum capability of 20 watts and 14 dBi antennas.  
      L-Band Not tested yet. Gound station uplink not installed yet.  
  Downlinks   Summary Low speed OK. High speed critical failure.  
      VHF 145.825MHz Strong signals received from satellite's monopole antenna. -108 dBm signals received on 'rubber duckie' antenna for hand-held radio. Signals even heard inside cars! Turnstile satellite antenna not used yet.  
      UHF 436.25MHz Good signals received from satellite's monopole antenna. Signals clearly heard on 'rubber duckie' antenna for mini-hand-held radio. Turnstile satellite antenna not used yet.  
      S-band TV Works well giving noise free TV images for elevations above +- 30 degrees. Transmitter only comes on if started with high battery voltage = charging with other transmitters off.  
      S-band data Appears to have failed after three uses. Exciter in S-band modem seems to have failed. All options have been tried to get link operating. Maybe more exist? This link uses the same TX PA and antenna as the TV link which works OK.  
  ADCS   Summary ADCS (Attitude control system) Needs work  
      Torquers OK  
      Reaction wheels Two wheels work (pich and yaw). The two wheels with brushless motors draw current but don't turn. Possibly an electronic commutation problem on the shared PCB  
      Coarse sun sensors OK except for intermittent +X sun sensor  
      Fine yaw sensor OK  
      Fine pitch/roll OK  
      ACP OK - T800 ACP (Attitude control Processor)  
      ICP OK - 8051 Interface Control Processor  
      Libration damping OK  
      Attitude estimator Not yet working as planned. The reason is not known (else it would be fixed). Not all sensor and estimator states were visible to telemetry on initial software. This is being upgraded (in spite of compiler problems) to get more diagnostic information.  
      Fine controllers These depend on the attitude estimator so don't work adequately yet.  
      Coarse yaw controller OK. This can maintain the relative sun yaw angle to within a few degrees and is a temporary controller to enable forward scanning TV to be taken while the fine controller is being corrected.  
      Polarities Polarity errors with some sensors/actuators were made in integration and had to be resolved through in-orbit tests. These have been done.  
  RAM Disk   Summary OK  
      Description The 64Mbyte static RAM disk works well, and runs the file system. It stores uploaded files and WOD data, and captures and reads out images on demand.  
  OBC1   Summary OK  
      Description OBC1 works well except for crashing about every 3 days, often at the South Atlantic Anomaly. Software upgrades are being developed to fine-tune behaviour so the watchdog on the OBC1 will help it re-instate satellite status after a crach.  
  OBC2   Summary OK, Software not ready  
      Description OBC2 has been booted and reactes normally. Full flight software for OBC2 has not been completed, so it is not ready for use. It has a 386SX instead of the 80188 in OBC1, so has greater speed and processing capability.  
  TV Camera   Summary OK  
      PAL camera Has 90 degree field of view & approx 1km pixel size. Standard colour TV camera.  
  Imager   Summary Looks OK but can't get data down at full speed.  
      Comment Imager evaluation has been severely hampered by malfunction of the high speed (40Mb/s) data downlink. The imager produces 3490*3 bytes per image line. At 9600 bd, we can download about 400 kbyte in a pass = 40 image lines. To speed evaluation we download a coarse image (350 x 350 pixels) and then select subsections of the image for full resolution download. Processed image subsections look excellent. Some samples may be released +- 15 July.  
      Mechanics OK. Has rotated and aligned itself aimed on -Z axis. Position sensors OK.  
      Optics OK. Evidence is a single sharp but poorly contrasted image.  
      KITSAT-3 The copy of Sunsat's imager in orbit on KITSAT-3 is producing excellent images. See  
  Laser retros   Summary OK.  
      Comment Sunsat has been tracked by numerous NASA SLR stations. Science campaigns are waiting till the GPSs and ADCS are working well.  
  GPS   Summary OK. Problems with OBC1 capturing data.  
      Comment The Turbo-Rogue is working and has produced navigation solutions. Between 20% and 70% of data packets are being corrupted by Sunsat's OBC1 due to interrupt overload. Software solutions are being investigated while the attitude estimation problem is being attended to.  
  School Xpts   Summary OK. Used little  
      Comment The experiments appear to be working but there has been little time to monitor them while attempting to resolve other ADCS and payload issues.  
  Amateur Radio   Summary SUNSAT Oscar 35 (SO - 35) is OK. Parrot software planned for August  
      Mode B Sunsat is activated on Sundays for Mode B (UHF up, VHF down) Amateur use. The audio output from an uplink NBFM receiver is fed to the NBFM VHF transmitter which is permanently keyed, producing strong signals on hand-helds. The transponder is over-busy on South African passes. It will be activated for two European and two N. American passes on Sundays also. We are power limited in the 12h00 orbit. When the orbit approaches dawn-dusk, every pass over land may be able to be supported. The parrot is delayed till +-August by software.  
  Flight software   Summary OK but needs extension  
      Comment Personnel shortage recognised before shipping led to Sunsat being launched without a fully commissioned software suite. We still suffer the consequences and are short of software engineers. Hardware problems (eg high speed data link) have placed increased demands on software improvements to add image correction and compression.  
  Ground Station        
  UHF downlink   On 4.5 m dish antenna Excellent - usually noise-free from horison-horison using 4.5m tracking dish with LHCP feed for RHCP reception. Normal signal level is -100 dBm (S7 on receiver)  
      Yagi's and helix Using tracking Yagi's, signal is good for 90% of pass, but sometimes noisy and swapping between antennas, needing a diversity switch. Best Yagi normally better than 9-turn 13 dBi helix.  
  VHF downlink   Yagi's Excellent - nearly noise-free from horison-horison.  
  S band TV downlink   4.5 m dish TV is excellent, normally noise-free (no sparklies) above 30 degrees elevation. Dish normally tracks open-loop from orbital predictions, sometimes using conical scan to correct initial timing error. A 35-K S-band LNA is installed on the S-band feed. G/T needs to be verified, but seems good enough.  
  S band data downlink   4.5 m dish Data never received from Sunsat. S-band data link failed after 3 operations that were received well by Overberg's 4.5 m antenna.  
  4.5 m dish   Status This is being used for UHF downlinking. The UHF and S-Band feeds have to be swapped when needed. A dual-band feed would be convenient, but we don't want to degrade S-band G/T  

Last Updated on 7/6/99
By Garth Milne