[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Satellite BEACON Texts Ideas

Satellite Builders BEACON info:
    Most satellites include an occassional BTEXT in their downlinks
for updating users with recent summary information about the bird.  In
the future, it might be useful to consider using a format that will
be captured and displayed on the front panel of any of the thousands
of digital handheld or mobile radios to maximize the dissemination of 
this sample  information to casual users and new user/demos.
These radios ignore most packets and only capture specific UI packets. It
might be handy to identify the most useful such formats recognized by
these radios and other APRS software for possible downlink applications:
   STATUS:     A one line packet summary of satellite status
   BULLETINS:  A multi-line format captured by all
   TELEMETRY:  A one line 5 analog channel and 8 bit summary format
   NASA OLEs:  A one line update of NASA One-Line-Elements.
   POSITION:   Includes LAT/LONG/CSE/SPD/ALTITUDE, etc if GPS is onboard
Although there are many dozens of APRS formats and the spec is over 
100 pages, the above four will probably be sufficient.  Details follow:
STATUS:  Status packets are any packet beginning with a ">".  All radios
will capture this, and save the last such STATUS per satellite.  (one
each).  The HT is limited to 20 bytes and the mobile is limited 
to 32 bytes., but APRS software will capture 67.     Example:
   NEWSAT>QST:>This packet will be displayed **
BULLETINS:  A multiple line bulletin may be transmitted as follows:
   NEWSAT>QST::BLN1GROUP:These bulletins can contain multiple lines and 
   NEWSAT>QST::BLN2GROUP:each line can be as long as 64 characters, but
   NEWSAT>QST::BLN3GROUP:the display on the HT truncates to 45 chars.
   NEWSAT>QST::BLN4GROUP:The lines are sorted on receipt by the numerial
   NEWSAT>QST::BLN5GROUP:in the BLN# format.  Also, the "GROUP" can be
   NEWSAT>QST::BLN2GROUP:any desired sub-group for filtering if needed.
TELEMETRY:  The brief APRS telemetry packet includes five 8 bit analog 
values and 8 single status bits.  Though this is not sufficient for most 
satellites, it can be used to give a "quick look" of the top five values 
of interest, and on/off status of several experiments.
The first field is a serial number followed by the five 3 byte decimal
telemetry values between 000 and 255 (although values to 999 are 
permissible).  On receipt, most APRS software will even do engineering 
unit conversion to custom values.
ONE-LINE-ELEMENTS:  There is also a format for transmitting NASA 
One Line element sets, which will auto-update all APRS satellite 
tracking software with the latest KEPS in a single packet.
POSITION:  For any satellies with GPS on board, there are also 
several APRS formats for position, direction, speed and altitude, etc.  
Some as short as a 6 digit grid square, or 9 bytes including position 
to the nearest foot, or, or a longer human readable 26 byte format.

AX.24 HEADER:  Oh yes, the format must be addressed to a typical BEACON
type address such as CQ, QST, ALL, BEACON, APRS and a few others...
I hope this information will be helpful in the design of future easy-sats.

de WB4APR, Bob  @amsat.org

Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org