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[jamsat-news:1284] * SpaceNews 12-Jun-00 *

* SpaceNews 12-Jun-00 *

BID: $SPC0612


		 	  MONDAY JUNE 12, 2000

The SUNSAT-OSCAR-35 satellite has recently been transmitting telemetry
information in the form of AX.25-protocol packet radio frames on a
downlink frequency of 145.825 MHz.  As Johann Lochner explains, the
spacecraft 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.  

[info via Johann Lochner, ZR1CBC]

* RS-15 NEWS *
Ken, N1WED reports copying RS-15 on June 6th during pass # 22430, a pass
North to South almost straight down the Mississippi River, that produced
a return signal of a solid 5-5.  It was noted this occurred during the
approach phase and lasted for about four minutes at a range of 2100
statute miles.  Ken called CQ and recorded the pass, but received zero
responses.  After reaching perigee to his groundstation, SSB dropped
to zero, though a faint FM signal could still be received.

[Info via Ken, N1WED]

Bent Bagger, OZ6BL, has uploaded version 1.5 of PB and PG for Linux to
metalab.unc.edu.  The file name is pbpg-1.5.tar.gz.  Bent has placed
the file and the accompanying lsm-file in /incoming/Linux directory.
The target directory is /pub/linux/apps/ham.  The file may also be
downloaded from ftp://ftp.amsat.org/amsat/software/Linux/pbpg-1.5.tar.gz.
The updated documentation is found in the file named README.

This is a patch release.  Sometimes PB would send requests for directory
fills when it was not needed.  This has been fixed.  It was due to erroneous
handling of fragmented broadcast directory entries.

PB and PG for Linux are programs used for download from and upload to
digital satellites (Pacsats) supporting the FTL0 protocol.  This software
allows groundstations to directly communicate with the Microsat series of
satellites.  It provides a curses (ncurses) based user interface, and
features automatic directory fill requests, and simple rules-based file 
download requests.  This version of the programs will work with kernel
revisions 2.0.24 or higher.

[Info via Bent Bagger, OZ6BL]

Thanks to all who sent news items and/or messages of appreciation to
SpaceNews in recent weeks, especially:

		N1WED				W8JSA

Comments and input for SpaceNews should be directed to the editor
(John, KD2BD) via any of the paths listed below:
WWW:        http://www.njin.net/~magliaco/
MAIL:       John A. Magliacane, KD2BD
            Department of Engineering and Technology
            Brookdale Community College
            765 Newman Springs Road
            Lincroft, New Jersey 07738
INTERNET:   kd2bd@amsat.org, magliaco@email.njin.net

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