Because I doubt most of the average OF users watch the IRC channel like it's the world cup, and even fewer of you read my clever git commit comments, I thought I would document a few of the new (small) features I've added. over the last few months.
CSM High-Gain S-band Antenna Tracking and Signal Strength.
A schematic of the HGA system is shown below, taken from the CSM systems handbook.
Previously, only the manual mode of the HGA worked and the signal strength was fixed at 75%. Now, both the auto track mode, and the reäcquire mode work.
There is a table in the image above that describes the antenna system logic based on the mode and beam width switches:
There are three servo axes through which the antenna is driven. Antenna pointing vector elevation is less than 45°, the antenna is just moving in the azimuth and elevation directions (A and C servo respectively), but occasionally the B axis servo will step in "look left or right" as the target (Earth) tracks near the pole(antenna boom arm vector). This eliminates the need for extremely high A axis angular rate. If the elevation servo is above 45°, than the servos act in an X-Y mode with the B-C servos. All the while however, there is a negative feedback gain applied to the B servo from the A-axis' error, the goal of which is to reduce the "look left or right" angle to zero, by means of rotating the azimuth servo.
Reacq mode is similar to the auto mode, with the exception that upon signal loss, it reverts to manual mode and drives the antenna to the rotary switch direction.
For signal strength, we're now using a Friis equation-based signal strength model. for the S-band gauge in the CSM, 0-100% is -130dBm to -50dBm. Signal strength is now a function of: distance, frequency, power, tx and rx gains.
Tracking is accomplished by an error signal, which is generated by difference in the array elements, which is turned into servo commands by means of a proportional controller (with appropriate feedback).
CSM OMNI S-band Antenna and Signal Strength.
Also updated to use a Friis-based model, with a much more realistic antenna radiation polar.
LM Steerable S-band Antenna and Signal Strength.
This is essentially the same as the CSM but with only two axes and no beam or alternate auto modes.