Skimsat study to put satellites into very low Earth orbit

The cost of Earth observation could be reduced considerably with Skimsats, a new class of spacecraft subject to research being carried out by Thales Alenia Space and Qinetiq.

Thales Alenia Space

The companies have signed a study contract with the European Space Agency to advance the small multi-mission satellites being designed to operate in Very Low Earth Orbit (VLEO).

The Skimsat concept was proposed in a 2016 paper titled Skimsats: bringing down the cost of Earth Observation. In it, former Thales Alenia Space employees Andrew Bacon and Ben Olivier (both now at Space Forge) said ‘The Skimsat concept is based upon the idea of that the closer you are to a target, the smaller an imaging payload can be, leading to reductions in overall satellite size and cost.’

Challenges to Skimsats include the effects of drag, damage to optical surfaces caused by higher densities of atomic oxygen found at low altitudes, and higher rates of orbital drift.

“One of the things we’ll do with Qinetiq is optimize the structure of the satellite in an attempt to reduce that drag, and that means we can optimize our propellent budget,” said Stephen Mellor, product manager at Thales Alenia Space UK.

Mellor added that accommodating equipment brings changes the frontal area of the Skimsat, which changes the impact of drag and the satellite’s propellant budget.

“The study provides us with an opportunity to do that exercise where we do some tradeoffs with equipment, we look at the impact of various changes to the structure in terms of the platform and what that means for the business case as well: how long will the satellite last…what size of telescope can we accommodate. These are some of the tradeoffs we can do,” Mellor said.


Payloads using the multi-mission Skimsat platform will be identified as part of the study for an In Orbit Demonstration to show applications in VLEO prior to the first commercial mission.

“Things have moved on over the years with small satellites in LEO [Low Earth Orbit] for 5-to-7 years,” said Mellor. “Although the launch costs will be lower with smaller launchers that we’ll get from the UK, ultimately we need to be targeting three years minimum for the platform lifetime.”

Mellor added that the nominal altitude for an in-orbit demonstrator will be 240km, the minimum being about 220km, and the maximum 260km.

“We will vary that depending on the solar cycle, which will define the density experienced at different altitudes.”

The study - funded under ESA’s Discovery Preparation and Technology Development (DPTD) activities - is being led by Thales Alenia Space in the UK and Qinetiq’s Space team in Belgium.

Skimsat stats

Length: 1.9m Wingspan: 3.2m Height: 0.5m (all figures mission dependent)