karn@bellcore.uucp (Phil R. Karn) (12/06/84)
AO-10 RTTY Format Delineated
On 3 Sep 84 a new beacon system was implemented on AO-10 which
included for the first time an RTTY transmission. This signal
coded key spacecraft operating conditions in a format convenient
for many Amateurs not equipped with the PSK decoders used by the
command stations and a fortunate few others. Now comes word on
how to decode the RTTY telemetry being heard both on Mode B
(145.810 MHz) at 15 and 45 minutes past the hour and on Mode L
(436.040 MHz) at 0, 15, 30 and 45 minutes past the hour.
According to command station VE1SAT/VE6, the so-called "Y" block
sent as RTTY is a version of the "Z" block telemetry send via
PSK. Thus many of the key operating parameters are now
available for general consumption to anyone who has 45 baud
baudot RTTY demodulation and display capability.
The exact baud rate is 50 rather than the 45 baud (60wpm)
standard but most electronic and mechanical machines equipped to
receive 45 baud will respond well to 50 baud. The AO-10 RTTY
telemetry is sent in FSK with 170 Hz shift and is standard
baudot (5-level) coded.
The following table provides the key to understanding the
transmitted information about the spacecraft operating
conditions. The parameters are organized and transmitted as six
rows of ten columns. For convenience we will label the rows "A"
through "F" and the columns 1 through 10 thus:
1 2 3 4 5 6 7 8 9 10
----------------------------------------------
A
----------------------------------------------
B
----------------------------------------------
C
----------------------------------------------
D
----------------------------------------------
E
----------------------------------------------
F
----------------------------------------------
Each of the 60 telemetry cells or channels is sent as a 1, 2 or 3
character numeric group such as "0", "16" or "165". Each block
of 60 is preceded by a narrative, the decimal date (day zero
equals 1 Jan 78) and several hexadecimal numbers. Your
key to knowing when the block of 60 begins is to watch for a
long series of space characters followed by numerous carriage
return/line feed sequences.
_________________________________________________________________________
Tlm
Row/ Meaning Equation Units
Col
_________________________________________________________________________
A1 Solar panel out and BCR input voltage n*150 mV
A2 70cm xmtr average power output (253-n)^2/2000 W
A3 70cm rcvr temperature (n-127)/1.82 C
A4 Nutation dampner temperature (inoperative) -
A5 BCR output and main battery voltage (n-10)*75 mV
A6 Special purpose xxxxxxxxxxxx -
A7 70cm xmtr temperature (n-127)/1.82 C
A8 14 volt rail current to xponder (n-15)*20.64 mA
A9 10 volt regulator voltage (n-12)*50 mV
A10 He tank pressure at hi pres regulator (n-34)*44.46 bar
-------------------------------------------------------------------------
B1 IHU temperature (n-127)/1.82 C
B2 14 volt rail current to magnetorquers -
and antenna relay (n-15)*4.128 mA
B3 BCR #1 status 0=Off; N>10=On -
B4 He tank pres at low pres regulator (n-37)*0.8 bar
B5 BCR temperature (n-127)/1.82 C
B6 10 volt regulator current (n-15)*4.128 mA
B7 BCR #2 status 0=Off; N>10=On -
B8 Not used xxxxxxxxxxxx -
B9 SEU temperature (n-127)/1.82 C
B10 Battery charge current (n-15)*10.32 mA
-------------------------------------------------------------------------
C1 Top photocell sensor 65 means sun normal -
to Z (spin) axis; -
20-30 nominal -
C2 Special purpose xxxxxxxxxxxx -
C3 Main battery case #1 temperature (n-127)/1.82 C
C4 Active BCR ouput current (n-15)*20.64 mA
C5 Bottom photocell sensor (same as C1) -
C6 Kick motor strut temperature (Inoperative) -
C7 Main battery case #2 temperature (n-127)/1.82 C
C8 Active BCR input current on 28 volt line (n-15)*10.32 mA
C9 Spin rate {if n<139, r=(139-n)*0.8+20 rpm
or {if n>=139 r=508/(n-116)-2 rpm
C10 24cm rcvr AGC {if n<100 AGC=0 dB
or {if n>=100 AGC=(n-100)^2/189 dB
-------------------------------------------------------------------------
D1 Auxillary battery temperature (n-127)/1.82 C
D2 Solar panel #6 current (n-15)*4.128 mA
D3 2m xmtr average power output (200-n)^2/2000 W
D4 He tank temperature (n-127)/1.82 C
D5 Solar panel #1 temperature (n-127)/1.82 C
D6 Solar panel #5 current (n-15)*4.128 mA
D7 70cm rcvr AGC (n-83)^2/1000 dB
D8 70cm xmtr temperature (n-127)/1.82 C
D9 Solar panel #3 temperature (n-127)/1.82 C
D10 Solar panel #4 current (n-15)*4.128 mA
-------------------------------------------------------------------------
E1 Special purpose xxxxxxxxxxxx -
E2 70cm rcvr temperature (n-127)/1.82 C
E3 Solar panel #5 temperature (n-127)/1.82 C
E4 Solar panel #3 current (n-15)*4.128 mA
E5 14 volt regulator voltage (n-10)*61.5 mV
E6 Wall temperature in arm #3 (n-127)/1.82 C
E7 Top surface temperature of arm #1 (n-127)/1.82 C
E8 Solar panel #2 current (n-15)*4.128 mA
E9 Internal 9 volt bus from transponder (n-10)*50 mV
E10 Wall temperature in arm #2 (n-127)/1.82 C
-------------------------------------------------------------------------
F1 Bottom surface temperature of arm #1 (n-127)/1.82 C
F2 Solar panel #1 current (n-15)*4.128 mA
F3 Special purpose xxxxxxxxxxxx -
F4 Wall temperature in arm #1 (n-127)/1.82 C
F5 N2O4 tank temperature (n-127)/1.82 C
F6 UDMH tank temperature (Not used) -
F7 Auxillary battery voltage (n-10)*75 mV
F8 Central supt cylinder temp near arm #1 (n-127)/1.82 C
F9 Earth sensor temperature (n-127)/1.82 C
F10 Not used xxxxxxxxxxxx -
-------------------------------------------------------------------------
NOTES
B1: IHU = Integrated Housekeeping Unit; the computer
B3: BCR = Battery Charge Regulator
B4: He = Helium
B9: SEU = Sensor Electronics Unit
C8: Direct from solar panels
F5: N2O4 is nitrogen tetroxide; the propellant oxidizer
F6: UDMH is unsymmetrical di-methyl hydrazine; the propellant fuel
Compiled 04Dec84 by WA2LQQ with VE1SAT, KA9Q, DB5ER, R.Gape