PCsat Telemetry

US Naval Academy Satellite Lab, Bob Bruninga, WB4APR

The Worldwide Internet APRS Data Collection System: The graphic Telemetry links below give the complete telemetry as captured by the worldwide APRS Internet system and archived on Steve Dimse's FINDU.COM database. This system demonstrates the power of using internet linked amateur satellite ground stations around the world to capture live telemetry data for use anywhere. This first image is of the overall PCsat Telemetry System so that you can see how the data is organized into Voltages, Currents, Temperatures and Switch status.

Telemetry Description: The data shown in the graphics links below is 100 days worth from 1 December 2001 to 10 March 2002. The data is presented in its raw form with each telemetry value showing as a color dot in the upper portion of each graphic. The middle green/red color bars show the ON/OFF status of the 13 telemetry bits. Red means ON or "0". The large lower section shows the count of the 001-to-999 telemetry frame counter. It gives a good view of the continuity of the data over ground stations and the occurrence of any random resets that would reset the couter to 001.

NOTE: These plots cover exactly 100 days of data, but the data is presented as contiguous data points, not linearly with time. So the Side A telemetry appears longer because more data points are captured on the larger number of IGate stations monitoring the 145.825 downlink than on the USA-only monitoring stations on 144.390. Also, any data that may be missing will simply concatenate the data rather than showing a gap. Thus the TIME axis only has two known points, The start on 1 Dec and the end on 9 March. Further there may be lots of data missing from the A side plots because you can see the time that the GPS was turned ON is significantly different between the A side and the B side, though they both read the same telemetry value. So be careful of significant distortions in the horizontal TIME axis.

Data Analysis During this period, there are three general situations of interest. First is the declining power budget in early December due to the combination of a maximum 35% eclipse period, during the Winter Solstice and our failed -Z solar panel which points generally up in the southern Hemisphere. Next is the period of full Sun from about 7 to 23 January, followed by another period of maximum 35% eclipse in February leading to a minimum eclipse cycle of 15% on March 7th at the end of the data.

BINARY BITS: In all of the plots below, you can see the status of the 8 command bits. The first two we try to keep always RED meaning the UHF receivers are both commanded OFF. The 3rd bit is the GPS which was used during full sun between 7 to 21 January and the 6th bit toggles the GPS data between MITEL and NMEA format. Any toggles in the other bits are insignificant.

PCsat side A Telemetry - Primary user transponder on 145.827

  • Frame 00 Currents Notice the drift upward during full sun of the "0" current values due to higher temps.
  • RED +XA Array Current
  • BLUE +Z Array Current <== some apparent loss of current for our Space Qualified Cells
  • GREEN +YA Array Current <== apparently same degradation of our plastic covered cells
  • BLACK -XA Array Current

  • Frame 01 Temperatures Cyclic Temps are probably due to data aliasing since it is 64 cycles in 100 days.
  • RED +Y Array Termperature
  • BLUE Battery A Temperature
  • GREEN XMTR A Temperature
  • BLACK +Z Array Temperature <== Note change in symmetry due to change in Southern Hemisphere sun

  • Frame 10 Temps/Currents
  • RED +X Array Temperature
  • BLUE Stack A Temperature <== Note the Temp rise on A stack while GPS is on
  • GREEN -YA Current
  • BLACK Battery A Charge Current <== Note constant values are nominal discharge in no sun

  • Frame 11 Voltages
  • RED A Battery Voltage <== Note slight degradation of A battery relative to B
  • BLUE B Battery Voltage <== And lack of full charge ever in last month
  • GREEN A XMTR Power Output
  • BLACK +8 Bus Voltage
  • GRAY +5 Bus Voltage (213)

    Data Analysis: ALthough we have not thoroughly digested the trends in the data, there are a few observations we find interesting and worth of further analysis:

  • Lack of symmetry around the full sun period even though the geometry of eclipse periods is symetric.
  • Lack of symmetry could simply be missing data causing an apparent compression of the time axis
  • Some apparent degradation of our plastic covered terrestrial solar cells
  • Similar apparent degradation of our Space rated Glass covered +Z cells...
  • Wider fluctuation in temps over time, possibly due to slower spin rate?
  • Battery run-down during full sun due to GPS being on all most of the time.
  • Apparent 1.5 day cyclic pattern probably due to aliasing of ground stations access times?

    PCsat side B Telemetry - North American downlink on 144.39 (only special travelers)

  • Frame 00 Currents Notice the drift upward during full sun of the "0" current values due to higher temps.
  • RED -Xb Array Current
  • BLUE -Z Array Current <== Definately Zero output from -Z array
  • GREEN -YB Array Current
  • BLACK +XB Array Current

  • Frame 01 Temperatures Cyclic Temps are probably due to data aliasing since it is 64 cycles in 100 days.
  • RED -Y Array Termperature <== lack of symetry means that something has changed
  • BLUE Battery B Temperature <== since full sun. Maybe emissivity of Teflon coating?
  • GREEN XMTR B Temperature
  • BLACK -Z Array Temperature <== Note change in symmetry due to change in Southern Hemisphere sun

  • Frame 10 Temps/Currents
  • RED -X Array Temperature
  • BLUE Stack B Temperature
  • GREEN +YB Current
  • BLACK Battery B Charge Current <== Note constant values are nominal discharge in no sun

  • Frame 11 Voltages
  • RED A Battery Voltage <== Note slight degradation of A battery relative to B
  • BLUE B Battery Voltage <== And lack of full charge ever in last month
  • GREEN B XMTR Power Output
  • BLACK +8 Bus Voltage
  • GRAY +5 Bus Voltage (213)



    Return To:

    PCsat Main Page

    Site Map