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AO-7 tlm.




Apologies folks, forgot to sign the following 'parable' - so you wouldn't have known who to blame.

Crikey, my 'periodic Altzheimers' is accellerating ...

73 John.   <la2qaa@amsat.org>
..........................................................................................

Ron,
       (and any other interested parties) ... Be aware that 98% of the AO-7 tlm is rubbish. The satellite is has been sending incorrect frames for several years. You can check this yourself by monitoring the 6D parameters.

They should be either 649, 650 or 651. If they are not, the tlm is incorrect.

It has to do (mainly, but not only) with the power budget ... this is why it is imperative certain 'clowns' stop hitting it with too much power. It is essentially a QRP satellite and the 'gentleman' who proclaimed one needed an 80w BRICK, last year on this reflector. is wrong, wrong, wrong.

The following is a recent e-mail to me from Jan King, AO-7's project manager.

(I maintain a rather large database regarding this satellite and have just about all the information available on AO-7 in several maps).

A *LOT* of information is contained on/from The AO-7 Resource Page if one cares to follow the links.

EU-Amsat (c/o SV1BSX) maintains the distance records for AO-7.

The foll0wing is an e-mail from Jan.

73 John.   <la2qaa@amsat.org>
.................................................................................................

John.

Telemetry received may be good or bad. You can determine if the telemetry is good by the 6D value. It is the reference voltage for the analog TLM system and it should be around 50. If not, then the remainder of the telemetry will be incorrect. 

(clip) Jan King, W3GEY notes that AO-7 had (has?) a very sensitive receiver and a good uplink antenna. 5 watts EIRP should provide a good downlink (clip).

 Amplifiers are not required for the uplink. Excessive uplink power may be cause FMing of the transponder and may be causing the input voltage to the regulator that provides 6D to fluctuate causing all telemetry to be bad. AO-7 is almost certainly running only off the solar panels. It is very likely to be on only when in the sun and off in eclipse. Since it is resetting each orbit it may not come on every time. Reports of hearing the beacon just as it comes out of eclipse would be particularly interesting.

1. Speculation that long term chemical changes in one or more battery cells have led to increased cell resistance enabling the spacecraft to operate while in sunlight are correct and

2. Reports indicating that beacons, telemetry systems, and possibly transponders are operating

Then

The prognosis for long term spacecraft operation are excellent.

Channel Measured Parameter Measurement Range Calibration Equation (Preliminary)
1A Total Solar Array Current  0 to 3000 ma  I = 29.5 N (ma)
1B +X Solar Panel Current  0 to 2000 ma  I = 1970 - 20N (ma)
1C -X Solar Panel Current  0 to 2000 ma  I = 1970 - 20N (ma)
1D +Y Solar Panel Current  0 to 2000 ma  I = 1970 - 20N (ma)
2A -Y Solar Panel Current  0 to 2000 ma  I = 1970 - 20N (ma)
2B RF Power Out 70cm/2m  0 to 8 watts  P = 8(1 - 0.01N)^2 (watts)
2C 24 Hour Clock Time  0 to 1440 min.  t = 15.16N (min)
2D Battery Charge/Discharge  -2000 to 2000 ma  I = 40(N - 50) (ma)
3A Battery Voltage  6.4 to 16.4 V  V = 0.1N + 6.4 (volts)
3B Half-Battery Voltage  0 to 10 V  V = 0.10N (volts)
3C Bat. Chg. Reg. #1  0 to 15 V  V = 0.15N (volts)
3D Battery Temperature  -30 to +50 deg. C  T = 95.8 - 1.48N (deg. C)
4A Baseplate Temperature  -30 to +50 deg. C  T = 95.8 - 1.48N (deg. C)
4B PA Temp. 2m/10m  -30 to +50 deg. C  T = 95.8 - 1.48N (deg. C)
4C +X Facet Temp.  -30 to +50 deg. C  T = 95.8 - 1.48N (deg. C)
4D +Z Facet Temp.  -30 to +50 deg. C  T = 95.8 - 1.48N (deg. C)
5A PA Temp. 70cm/2m  -30 to +50 deg. C  T = 95.8 - 1.48N (deg. C)
5B PA Emit. Current 2m/10m  0 to 1167 ma  I = 11.67N (ma)
5C Module Temp. 70cm/2m  -30 to +50 deg. C  T = 95.8 - 1.48N (deg. C)
5D Instrument Sw. Regulator Input Current  0 to 93 ma  I = 11 + 0.82N (ma)
6A RF Power Out 2m/10m  0 to 10,000 mw  P = (N^2)/1.56 (mw)
6B RF Power Out 70 cm  0 to 1,000 mw  P = 0.1(N^2) + 35 (mw)
6C RF Power Out 13 cm  0 to 100 mw  P = 0.041(N^2) (mw)
6D Midrange Telemetry Calibration 0.500 V  V = 0.01N(0.50 +/- 0.01) (V)


AO-7 telemetry format:

1aa 1bb 1cc 1dd
2aa 2bb 2cc 2dd
3aa 3bb 3cc 3dd
4aa 4bb 4cc 4dd
5aa 5bb 5cc 5dd
6aa 6bb 6cc 6dd
Hi Hi
then these data are valid when 6D is one of 649, 650 and 651.

73 Jan   W4GEY/VK4GEY
...........................................................................................

> From: w7lrd@comcast.net
> To: AMSAT-BB@AMSAT.Org
> Date: Sat, 10 May 2008 18:41:15 +0000
> Subject: [amsat-bb] AO7 telemetry
>
> Hello
> Why does the telemetry on AO7 work sometimes? I ususally take a quick listen, also does it respond to any comands. In my opinion it's the best satellite we have up there! You can actually talk to someone for a reasonable amount of time.
>
>
> --
> 73 Bob W7LRD
> AMSAT member 28498
> Seattle

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