Hello!, First off, I'd like to say I had a blast at the 2015 AMSAT Symposium. It was a lot of fun and I know that the rest of the VT team really appreciated the warm welcome from everyone.

Drew and I got to talking at one point after the Banquet and he re-kindled an interest in something for me. He posted a while back about how the downlink for AO-73 is in the passband of FO-29's uplink, and that the PSK can be heard at times when monitoring FO-29's downlink. I'd like to do a bit more analysis using STK to predict when an 'accidental crosslink' might occur allowing a telemetry decode of AO-73 via FO-29.

Right now I'm using a simple model for all of this where I'm treating each satellite as a single point in the sky. The first question I'm asking (via STK simulation profiles) is when can the two "points in the sky" see each other when not blocked by the curvature of the earth. The next question I will ask of the great and glorious STK is when can the two "points in the sky" see each other AND when can the point in the sky that is FO-29 see the point on the ground that is the VT Ground Station.

When the second question yields accesses in time when the two spacecraft can see each other and FO-29 can see the VTGS, then I have a window to schedule the VTGS for this experiment.

The next trick will be accounting for doppler between the two spacecraft (via range rate info from STK for the two points) to determine where exactly in FO-29's uplink passband the AO-73 signal will fall. Then account for the Linear inverting transponder offsets, then account for doppler between FO-29 and VTGS. Also, the signal spectrum will be inverted due to the transponder, but we can "re-invert" in our GNU-Radio flowgraph to account for that.

End result should be an access window at VTGS along with a predicted doppler curve for tuning at VTGS, ultimately getting us to an AO-73 tlm decode via FO-29.

My question for the group concerns the antenna patterns for FO-29 and AO-73. I'm trying to plan ahead for refining the access windows for when to actually conduct this experiment by doing a bit more than treat each satellite as a "point in the sky." Does anyone have any info on the actual antenna pattern for FO-29? Along with this, I remember reading somewhere that FO-29 has an attitude control system. Is this system still operational and if so, what is the "target attitude." I'm trying to get a sense of the antenna patterns for the two spacecraft and their orientations to identify "sweet spots" where antenna patterns might align positively. On the other hand it will be good to know when we have an access window but one of the spacecraft is in the null of the antenna pattern of the other spacecraft. For AO-73 I'm assuming simple whip antennas. I know it doesn't have a positive attitude control system, but if memory serves I think it has a bar magnet and the spin from the anodized bars imparted on it that should give me a sense of its orientation at particular times.

Thanks in advance! -Zach, KJ4QLP