A photo of the Sahara Desert with its reddish glow serves to prove that Estonia’s first satellite’s onboard camera is working. At the same time, the satellite-team is troubled by the stormy Sun, able to deal a fatal blow to the tiny space traveller.
Estonian satellite EstCube-1 sends first picture of Earth
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The picture, with Italy under a carpet of clouds and the Mediterranean and Northern-Africa seen more clearly, was taken by the EstCube-1 camera at height of 670 kilometres, over Croatia, last Wednesday at 13:12 pm, Estonian time.
As communication with the satellite is only possible as it flies over, using amateur radio lengths whish allow limited data flows, the final pixels of the EstCube debut photos only reached Tartu yesterday morning.
«With one data package, maximum 200 bytes arrive, making about a hundred pixels,» said the camera team leader Henri Kuuste, master’s student of computer technology at University of Tartu.
Why was the first picture not of Estonia? Mr Kuuste says the answer is pretty prosaic: «We didn’t choose what to shoot, it just happened to be a good overflight.» The aim being to test the camera, they seized the first opportune moment.
By yesterday morning, it was clear that the camera works faultlessly – as all other subsystems tested so far. Now, the camera is again switched off, waiting for EstCube’s main experiment: shooting a picture of a weight hanging from a nanocable, to be rolled out from the satellite.
«As the cable itself will not be seen, by shooting a picture of an aluminium cylinder at the end of it, it can be measured, if the cable has been rolled out and how far,» said Mr Kuuste. The main task completed, we can again start to think about pretty pictures and it is definitely desired to take a picture of Estonia, assured Mr Kuuste.
«It will be quite hard,» he said. «EstCube-1 visibly flies over Estonia about 11 times a day, but only every third day it is in the exact zenith. To take a picture, we should wait for a day when the satellite is in zenith, in daytime, and there’s not too much clouds.»
Mr Kuuste was satisfied with the first picture, but does not think it is perfect yet. «Some clouds were overexposed,» he admits.
Even though many cube satellites have cameras onboard, few of them have managed to shoot pictures with good quality. According to a team-member, University of Tartu astrophysics doctoral student Tõnis Eenmäe, EstCube’s picture is among the best taken by cube satellites – even when compared to the Hungarians’ MaSat-1, of the same size, tasked specifically with taking pictures of the Earth.
According to Mr Kuuste, many teams use devices meant for mobile phones, which tend to break.
Therefore, the EstCube team built a custom made camera system, using an industrial lens, avoiding plastic components and adding special filters.
Looking closely at the picture, a red dot may be seen in the space – evidently caused, in the camera’s memory, by being hit by some cosmic particle. Particles like that can destroy camera’s components. The Sun currently being very active and sending flares in all directions, there is reason to be worried.
«There is danger, definitely,» admitted Mr Eenmäe. «Even big satellites have been destroyed by solar storms.» The Estonian cube has no special protection against radiation.
There is a high probability that a crisis situation occurred, by something of this sort, last week. «The satellite was hit by something on Monday, during the strongest sun flare,» guesses Mr Eenmäe. «Something strange was going on with the electric systems processor, GPRS was not working.»
Luckily, the satellite still receives messages from the command centre, the problem being solved by a «restart».
EstCube-1
• EstCube-1 was launched, on board of European carrier Vega, on May 7th, early in the morning.
• The satellite’s scientific task is testing a component of a solar sail. The team believes this can be accomplished in after a few months.
• During the two initial weeks, the team has established a two-way communication with the satellite, successfully tested subsystems and updated software.