So, I've been having a mild amount of fun using my Python code to track the various recently launched cubesats, and especially SEEDS II, which I find to be really easy to receive. My script drives the frequency control on my FT-817, and allows me to get easy recordings that by just aiming my Arrow at the spot it tells me to. I record these onto my laptop, and then process them into spectrograms for fun. For instance, a couple of days ago, I got the following:
http://brainwagon.com/images/seeds2-tlm2.jpg
Each horizontal pixel is 1/50th of a second, making the width of each row 20 seconds, and the full set of SEEDS II housekeeping telemetry is about 100 seconds. If you work through the picture, you can confirm that I didn't make any mistakes when I copied the telemetry as:
JQ1YGU SEEDS G4 01DF37DF CF1 FFE 007 00A 000 000 009 007 ABE AAC A94 AEA 11 0000 0001 0001 0001 55DD B1 40 30
Using the documentation for SEEDS that is available online, I decoded this as:
Satellite Callsign: JQ1YGU Satellite ID: SEEDS Satellite Mode: G4 Satellite Time: 15703023 sec Li-ion Battery Voltage: 4.04 v Bus Voltage: 5.00 v Solar Cell 1 current: 0.78 ma Solar Cell 2 current: 1.11 ma Solar Cell 3 current: 0.00 ma Solar Cell 4 current: 0.00 ma Solar Cell 5 current: 1.00 ma Solar Cell 6 current: 0.78 ma Temperature Li-ion Battery 1: -1.41 degC Temperature Li-ion Battery 2: -0.53 degC Temperature Transmitter: -2.27 degC Temperature Receiver: -4.48 degC
So, here's the question. This was a nighttime pass over CM87, and we see that the satellite must have been in eclipse, as its solar panels are generating almost now power, and the temperatures are pretty low. Is this common for the cubesat during eclipse passes. It dawns on me that my inability to get it transmitting in SSTV or digitalker mode might be that I have been catching almost exclusively night time passes (curse my day job). Looking back through the list, I've seen housekeeping telemetry where the temperatures are 40 degC or even higher. Is the variation in temperature really that great? Is it just that the thermal mass being low causes relatively deep cycling?
Just thinking...
Mark KF6KYI