Aihnss.154
net.columbia
utzoo!decvax!ucbvax!ihnss!karn
Wed Oct 7 06:48:44 1981
UoSAT/Oscar-9 Operating
After some initial difficulties in getting modulation onto the
2-meter beacon, the command station in the UK has succeeded in getting
Uosat-Oscar-9 to transmit 300 baud ASCII telemetry.
I just heard a pass at my station in which the spacecraft did seem
to be sending 300 baud ASCII, although I did not have a a modem
connected to the receiver to decode it. The tones are 1200/2400 Hz,
which can be received with a Bell 202 (NOT 103) modem.
On the first orbit after launch yesterday, passing over the UK,
command stations were able to turn the 2-meter beacon on and off,
but were unable to get any telemetry modulation. Without this data,
there was concern over the attitude of the spacecraft, in that it
seemed likely that the sun was shining down on its top. Due to the
thermal design of the spacecraft, this causes lower-than-nominal
temperatures.
Without positive control shortly after launch, it was not possible to
attempt to command the spacecraft into a bottom-toward-earth attitude
until the next series of passes over ground command stations in the UK.
For those of you who asked, some Oscar-9 data follows.
You need an amateur 2-meter receiver and, ideally, a tracking program using
classical orbital elements as input.
2-meter beacon: 145.825 Mhz, 350 milliwatts, left hand circular
polarization. This is strong enough to be recieved with a hand-held
transceiver!
70-cm beacon: 435.025 Mhz, 650 milliwatts, LHCP. Has not been commanded
on yet, to my knowledge.
Orbit elements:
Epoch time: Tue Oct 6 07:26:14 1981 CDT
81279.51821950
Element set: 127
Inclination: 97.4687 deg
RA of node: 242.0175 deg
Eccentricity: 0.0003192
Arg of perigee: 317.0446 deg
Mean anomaly: 43.0536 deg
Mean motion: 15.09377490 rev/day
Decay rate: 0 rev/day/day
Epoch rev: 1
Semi major axis: 6916.24 km
Period: 95.40 min
Apogee: 550.07 km
Perigee: 545.65 km
This is a sun-synchronous polar orbit with 3AM/3PM descending and
ascending nodes, respectively. Passes are short: about 12 minutes,
maximum, for an overhead pass. If you don't have a tracking
program, then just put your receiver on 145.825 Mhz FM and squelch
it. Connect it to an omnidirectional antenna and listen.
Passes for today, October 7, for my station (near Chicago, IL) are
1:50-1:56pm CDT, to the east; 3:21-3:31pm CDT, almost overhead; and
4:57-5:03pm CDT, to the west. Listen during these times and you
should hear something. Doppler is plus and minus several kilohertz.
Phil Karn, KA9Q
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