In space, space is at a premium.
Launching a satellite is hugely expensive. Every kilogram it weighs and every cubic centimetre it takes up costs money. Spacecraft engineers have therefore had to become experts at miniaturisation – and nowhere is this more obvious than with the CubeSat concept.
CubeSats are a class of tiny spacecraft. They are based on cubes just 10cm along each side, and up to three can be joined together into a single satellite. Thanks to their diminutive size, they can easily piggyback on other launches that have spare capacity, or alternatively many CubeSats can be launched in one go.
The most ambitious CubeSat project to date is a European project called QB50, which plans to send 50 CubeSats into orbit in one launch in early 2016. This will be the largest number of satellites ever put into orbit on board a single rocket.
Each of the satellites will be built by a separate institution from around the world (including one – UCLSat – by UCL’s Mullard Space Science Laboratory). Up to 40 of them will sport sensors that can probe the properties of the upper atmosphere. The consortium providing the sensors is led by UCL MSSL, which will build 14 spectrometers that will analyse the relative proportions of different types of particles in the thermosphere.
The Ion & Neutral Mass Spectrometer, designed and built at UCL, prior to being attached to the CubeSat. The device is less than 10cm across.
As the orbits of the 50 satellites gradually decay, they will spread apart, giving a unique opportunity to measure the upper atmosphere in multiple locations at the same time, using the same type of instrumentation.
QB50 is an ambitious programme, and so a precursor mission using just two satellites is now underway. Launched on 19 June from the Russian space centre at Yasny, the precursor satellites have a UCL-built Ion and Neutral Mass Spectrometer (INMS, which measures atomic and molecular oxygen, along with molecular nitrogen) and a Flux (Phi) Probe Experiment (FIPEX, which detects atomic and molecular oxygen) procured from the Technical University of Dresden.
The two complete satellites for the QB50 precursor flight. THe satellite on the right has an Ion Neutral Mass Spectrometer, built by UCL, attached to its top surface. The satellite on the left has a Flux (Phi) Probe Experiment, designed by the Technical University of Dresden
As well as being very small, the instrumentation for the QB50 test mission had to be developed very fast, over a period of just a few months. Mission approval came in October 2013, and the completed satellites had to be delivered to the launch site in May 2014.
A further test of UCL’s miniaturisation technology will come with TechDemoSat, a UK satellite that launches on 8 July, and NASA’s Sunjammer mission in January next year.
Dhiren Kataria (right), the MSSL detector physicist behind the QB50 INMS instrument. Behind him, the CHaPS payload for the forthcoming TechDemoSat mission (based on the same technologies as QB50 INMS) being prepared for testing in a calibration chamber