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Re: Re: SUNSAT(SO-35) Telemetry

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.


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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