Re: [amsat-bb] Re: SUNSAT(SO-35) Telemetry

["Johann Lochner" <lochner@xxxxxxxxxxxxx>]

Hi Mineo,

 > What mean this sequence of numbers in SO-35 telemetry ?

The status and telemetry data formats follow the APRS standard.  A 
typical status message is shown below.  After the identifying > 
header, the onboard computer generating the message and its current 
software version is shown.  This is followed by the current uptime, 
reset cause (pwrn: power on, tcmd: telecommand, wdog: watchdog) and 
current onboard time.

 >OBC1v6: up=3/03:20:54, rst=pwrn, Sat May 27 11:27:12 UTC 2000

The telemetry message contain ASCII data, which can be displayed in 
human readable format by terminal software connected to a TNC.  One 
sample set (such as the four examples below) from a 25 entry circular 
buffer (containing entries numbered 0 through 24) is transmitted at 
approximately 9.59 second intervals (orbital period / 25^2).  When 
the buffer pointer wraps after 24, all entries are shifted towards 
24, by moving a fresh sample set into 0 (and discarding 24).  The 
buffer thus contains a history of samples from the last orbit, 
sampled at just under 4 minute intervals, with entry 0 being the most 
recent addition.

T#000,099,139,059,028,042,11110000
T#001,099,133,110,032,088,11111110
T#002,099,138,140,032,092,11110000
T#003,099,132,132,032,096,11111100

Telemetry data is identified by a T# header.  The message consists of 
7 fields, numbered 0 through 6.  The fields contain the following 
data: buffer pointer (0 in the first example above), battery state of 
charge (99 %), battery voltage (13.9 V), battery current (59 - 128 = 
-69, indicating that the battery is a net source of 690 mA; this 
field wraps at the extremes), battery temperature (28 °C), top plate 
sun sensor reading (42, an uncalibrated 8 bit value).  The last field 
indicates the state of the 8 solar panel strings (0: sourcing the 
power bus, 1: shunted, dumping energy).

Data in fields 1 to 4 is supplied to OBC1 at 60 second intervals.  
Fields 5 and 6 contain raw telemetry, sampled every 2.34 seconds.  
Possible aliasing, as well as the unsynchronized nature of the two 
data sources, should be considered when correlating fields.  

Kind regards,
Johann, ZR1CBC

+------------------------------------------------+
   JG Lochner  ESL, Universiteit van Stellenbosch
   e-pos:      lochner@ing.sun.ac.za
   webtuiste:  http://esl.ee.sun.ac.za/~lochner
+------------------------------------------------+

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