Small satellite constellations are “in-vogue” today with the promise of being faster, cheaper and fostering new technology developments in space. Where does “reliability” and “failure rate” come into this discussion? Traditionally the space sector has been “risk averse” for compromising satellite quality & reliability - obviously due to the traditional length of time, cost and importance of the satellite mission mainly applied to large geostationary type satellites and missions. Today, however, with the tipping point for small satellites moving from university led research projects into full-scale commercial development, the reliability of the small satellite constellations proposed for the Low Earth Orbit (LEO) and Medium Earth Orbit (MEO) is critical for the commercial success of the programme.
The new business models necessarily being used now incorporate the critical launch element as part of the overall process of getting the constellation into orbit and functioning as well as the traditional ground and space segments. This launch process could involve more risk due to the higher number of launches and potential launch failures can be brought into the business model since the constellation will be initially launched and deployed and then replenished with multiple follow-on launches.
Once the small satellites are in orbit (LEO/MEO) however, the reliability and lifetime are now key to the commercial viability and success of the project. How long does a small satellite last in LEO/MEO? The answer to this question depends upon a number of things such as the mission objective including lifetime, type of components onboard the satellite and orbital height of the satellites etc. For example, LEO extends from 300 km to 800 km and the satellite can last from a few weeks, months or to 4+ years.
So the question needs to be asked – “how much satellite testing should you do on the ground to ensure each small satellite in this constellation will work for its designed lifetime in orbit?”
Traditionally large satellites that are destined to GEO and last 15 years must be very reliable and survive the space environment at GEO. The small satellites in constellations at LEO and MEO have a design life typically of a few months up to currently 4 years maximum before being replaced and the space environment can be more severe or benign according to the orbit the satellite is placed into (radiation belts effects, solar radiation, eclipse frequency etc.). Traditional environmental testing for large satellites can consist of the following; Electrical functional checks, electrical integrity checks, equipment alignment/adjustment checks, mass properties (Mass and Moment of Inertia/Centre of Gravity) measurements, deployment checks (e.g. solar array wings, booms, antennas etc.), payload antenna RF testing, Electro-Magnetic Compatibility (EMC) testing, sine and random vibration tests, acoustic testing, propellant simulant loading/unloading, electrical performance tests, thermal cycling test, thermal vacuum test, satellite to simulated space/ground segment tests etc. the challenge for the "NewSpace" industry is how are these traditional tests adapted for the small satellite production rates whilst maintaining quality control and reliability?
So how do we adapt this traditional environmental test flow for small satellite constellations where the satellites can be produced and tested in very large quantities and at a very different manufacturing rate (weeks/months) than a single large satellite (normally 2 years for a large GEO comsat)?
This is the new challenge that has today not been fully answered and will have to be “trail-blazed” by the new constellations such as the 900+ satellite OneWeb constellation, where production/test rates are in the order of days not months!
Companies and organisations are now building this new small satellite constellation environmental test infrastructure next to their manufacturing facilities that has traditionally been located at a few key large test sites around the world (e.g. ETS, Noordwijk in the Netherlands, IABG, Munich in Germany, DFL, Ottawa, Canada and Intespace, Toulouse, France to name a few).
The challenge will require a meeting of minds of "traditional" and "new" space to ensure that these new small satellite constellations meet their proposed expectations.