HaloSat just after deployment from the International Space Station.  HaloSat is a CubeSat mission lead by Professor Philip Kaaret to search for missing matter by measuring X-rays from the halo of our Milky Way galaxy.   HaloSat and RainCube, a CubeSat from the Jet Propulsion Laboratory, are seen in the center. RainCube is in front of the Earth’s limb, while HaloSat has a gold thermal shield. The two CubeSats have identical dimensions while stowed and are touching when deployed, but not physically attached. They separated a few minutes after this photograph was taken. Parts of the ISS’s solar array are visible in the upper right. Credit: NASA