Wednesday, 28 February 2018

Imaging FLOCK 2E 4 near decay

In the early morning of 27 February 2018, I was imaging a rocket stage from a classified launch, the NOSS 3-4 r/b, when suddenly a very fast, flashing object entered the FOV, and I followed it as it looked interesting (it was so fast that in the first instance I thought it was a meteor). It turned out to be the cubesat FLOCK 2E 4 (1998-067 JH, #41487).

FLOCK 2E 4 is a cubesat that was released from Cygnus OA-6 in May 2016. It is currently in a 247 x 260 km, 51.6 degree inclined orbit, and from the imagery it is clearly tumbling. It is coming down fast, with several km/day, as it is close to decay. An analysis with SatAna and SatEvo predicts that it will re-enter in about a week, on or near 2018 March 6-7.

The diagram below shows how the orbital altitude changed since it was released at 400 km altitude from Cygnus OA-6 in May 2016:

click diagram to enlarge

FLOCK 2E 4 was built by Planet Labs and was one of the imagers in their FLOCK constellation. It basically is a small 9 cm telescope with a camera, and delivered imagery of the Earth's surface with a resolution of a few meters.

FLOCK cubesat (image: Planet Labs)

It is a very small object, the smallest I have managed to image in Earth Orbit so far. The body measures only 34 x 10 x 10 cm, and with solar panels deployed, the maximum dimension is 34 x 30 cm. A lucky capture!

The camera used was the WATEC 902H with a Canon FD 1.8/50mm lens.


Kevin White said...

Beautiful catch, and I love the graph. I've been monitoring Tiangong (like many others) and got interested enough to try to find a good graph that showed where the tipping point typically is (assuming there was one) for drag and expedited orbit decay.

You graph seems pretty linear up to about 350km, then the dive begins. I think from other graphs with less data I had estimated something closer to 200km. This is a relatively light satellite with pretty substantial flat surface area, and I'd imagine different surface profiles/mass would have different curve characteristics, but maybe this particular sat is perfect to probe where the density of the thermosphere starts having a measurable effect on an orbiting mass. Anyway, thanks!

Side question: has anyone been probing the estimated orbit where ZUMA would have been had it deployed as expected? There were a lot of forum posts and articles about eventually searching they sky for such, but I haven't heard anyone report results or even attempting a search.

SatTrackCam Leiden said...

@Kevin: I personally did several plane searches for Zuma, for orbital planes between 50-52 degree orbital inclinations. Nothing was detected.