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[jamsat-bb:5350] DECODING OF SUNSAT TELEMETRY


SO-35のデジタルテレメトリの解析法がSUNSAT HPに掲載されていました.
http://sunsat.ee.sun.ac.za/news/20000530.html#en

DECODING OF SUNSAT 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 ー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).

The 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.

                                                   [ZR1CBC 30/5/2000]


/EX
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Ochiai Takushi(落合 卓史) <jo2oxl@jarl.com>
QTH:静岡県駿東郡清水町
JCG#18009
GL#PM95KC
http://www3.justnet.ne.jp/~dxer/
tel & fax +81-559-31-6640
de JO2OXL _.. .  .___ ___ ..___ ___ _.._ ._..
73 TU VA __... ...__  _ .._  ..._._
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