Jan 29, 2010

NASA/Marshall Astronomy: SOFCAL downlink video

SOFCAL downlink video

May 5, 1997

Anyone with an ATV (Amateur Television Receiver) can pick up the video from SOFCAL at a range of 300 to 350 miles. The frequency is 426.25 Mhz (equivalent to about cable channel 55 or 56). These will be still shots and black and white. Note that the video will not provide any data from the science package, just video images of the Earth below as SOFCAL floats at the upper edge of the atmosphere.

People can hook an outside antenna to their cable box and feed it into their TV. The range will be about 300 to 350 miles from the balloon. Any amateur radio operator with a packet TNC (terminal node controller) can receive the automatic packet/position reporting system (APRS) data on 145.790 MHz. The data format is:

APRS telemetry packets


xxx is the sequence (or record) number in 3 digit ASCII

aaa is the solar panel temperature in degrees F multiplied by 10 ie 75.4 F is 754, The aaa is represented by 3 ascii encoded digits.

bbb is the ambient (air) temperature (same format as aaa)

ccc is the inside the package temperature near the CPU (same as aaa)

ddd is the battery charging current in amps multiplied by 100 ie 1.92 Amps is 192 Range is - 0.55 Amps (current being used) to 1.5 Amps (current going back into the battery)

eee is the current output of the solar panel (same format as ddd) with a range of 0 to 3.5 amps.

Digital bits are all ascii 1's.

The data format used by the telemetry page built into the APRS software is:


UNIT.deg f,deg f,deg f,amps,amps,x,x,x,x,x,x,x,x


BITS.11111111, Solar Panel Experiment Telemetry

You may look at a description provided by Tucson Amateur Packet Radio for more information.

Back to SOFCAL or the main balloon story.

Author: Dave Dooling
Curator: Bryan Walls
NASA Official: John M. Horack