Searching for SkyCube
Nine days ago, five objects were released from the ISS. NORAD assigned them tracking numbers 39567 thru 39571. One of them is certainly SkyCube, and it's the only one that transmits on 915 Mhz. We detected a clear 915 MHz signal near ISS the morning after SkyCube deployed, and a second time on an iSS pass over a different ground station later that afternoon.
Since then, those objects have drifted hundreds of miles apart, and thousands of miles from ISS. Each ground station can really only track one object at a time - unless they're close enough to fit into the station's antenna beam. And then you don't know which one you've detected.
Twice last week, a 915 MHz signal was detected by two different ground stations (Australia on 3 March at 10:46 UTC; California on 4 March at 21:57 UTC). Both signals came at times when 39570 was passing over the ground stations that detected them. That's suggestive, but not conclusive.
On Wednesday, NASA, Celestrak.com - and Satellite Safari - assigned identifications to objects 39567 - 71 in the order they were released from the ISS. Those identifications are surely wrong. The satellites swapped order since their release; they have different masses and sizes, so atmospheric drag affects them differently. On some passes, we may have been trying to communicate with the wrong object(s).
So how do we tell who is who? We've been in contact with the chief engineer of Lithuania's satellites, LitSAT-1 and LithuanicaSAT, deployed at the same time as SkyCube. Laurynas writes:
"We noticed NORAD associated numbers to the satellites according to the order they were released from the NanoRacks deployer. This is of course not accurate since sats have taken other positions in orbit. For Your notice, it seems that two Lithuanian birds have received good TLE references from german ham radio operator Mike Ruprecht, see his webpage. We are now almost continuously tracking our LituanicaSAT-1 with NORAD catalouge no 39568U with good results."
Mike Rupprecht's identifications are: LITSAT-1 = 39568, LITUANICA = 39569, UAPSAT = 39571. These identifications disagree with NASA's. At this point both may still be wrong.
The process is like trying to figure out who's who in a group of gnats flying around inside a football stadium, by listening to each gnat hum a different tune, for a few minutes each day. It's going to take a while to sort them out.
In the meantime
Many of you are amateur radio operators who've asked for information to help track SkyCube's beaconing signals. Here's what SkyCube should be doing:
Every 3 minutes, SkyCube broadcasts its telemetry at 915 MHz with BPSK modulation at 9600 baud. The data is in a single AX.25 packet containing human-readable ASCII text, prefixed and followed by 2 seconds of preamble. The entire telemetry "tweet" should last about 4 seconds, and repeat every 3 minutes.
Today, we are releasing the first public beta of Scott Cutler's SeeDeR software. It's a Windows program that can decode AX.25 radio transmissions using inexpensive USB software defined radio (SDR) devices. You can also download a pre-recorded sample of a SkyCube "telemetry tweet". This is what to listen for.
Finally, many of you are amateur astronomers. As Sky & Telescope mentioned, experienced satellite observers may be able to image the CubeSats with a CCD camera or even visually, with a large (16"+) backyard telescope and dark skies.
Please report any radio or optical detections to email@example.com. Please include the date/time of your observations, your observing location, and equipment used. Please include any images, SDR recordings, screenshots of waterfall diagrams, etc.
We'll continue efforts to locate SkyCube and establish communication this week. Patience and persistence are the name of the game. This is just the beginning.
-Tim, Scott, Rouslan, Mark, and the rest of team SkyCube