UNSW-EC0 takes a "selfie" of home
On the 19th of March, 2018 the Australian Centre for Space Engineering Research's cubesat, UNSW-EC0 at an altitude of 378km was enduring its 4651st orbit of the Earth since being deployed from the International Space Station last year when it was commanded to take a photo using the Nadir (Earth) facing camera. The camera is an integral component of the Attitude (orientation) Determination and Control Subsystem and is not optimised for delivering high resolution images but for detecting the whereabouts of the Earth in the field of view of the camera. This is done by detecting the Earths horizon and estimating it's center from the curvature. The decision to take a photo was made after the ADCS system was reporting that the detection of the horizon was failing.
In this photo we can see the Earth with a lot of cloud cover over the Great Australian Bite with the western part of the bite just visible towards the top left section of the Earth. The sun is the next obvious feature in this image with the 'black sun' effect on the CMOS camera showing. The camera is fitted with a fish-eye lens which causes the apparent change in the curvature of the horizon and at the top of the image, extreme warping of the UNSW-EC0's chassis. To the right of the image we can see burn wire which was initially stowing the communication antennas until deployment(LINK to deployment media release) when they were burnt through releasing the antennas and allowing communications to be established. The burn wire is fixed to UNSW-EC0 to avoid creating unnecessary space debris. In zero g there is nothing stopping the residual burn wire from floating in front of the cameras. The operations team suspect that this may be the cause of the horizon detection algorithm reporting errors and are now compiling commands to mask that area of the image out.
The photo is the first of a series of photos taken during the pass that began at approximately 3:39 pm local time at the UNSW Sydney ground station. It was taken just shortly after acquisition of signal was achieved with UNSW-EC0 when it was just beginning its south-west to north-east pass over the ground station and subsequently the photos taken in the latter part of the pass should have a better view of the South Eastern region of mainland Australia.
Due to the relatively large size of these photos compared to typical data downlinked from UNSW-EC0, a custom, connection-less mode of download similar to that used by video streaming services was developed. Combined with an automated ground station, the operations team need only check on the progress of these downlinks in the near future while we wait for the remaining photos to come down.
The "Selfie" taken by UNSW-EC0, looking back towards the Great Australian Bight
Location of UNSW-EC0 when the selfie was taken