The main initial study objectives were as follows:
Two of the above objectives were refined as the study progressed, i.e. in particular the spacecraft mass was increased to <300kg, whilst the total mission lifetime was increased to 5.25 years.
The mission requirements impose severe constraints on the payload and platform, which drive the mass, power and cost of the payload and spacecraft (limited by the fundamental limits of a very small satellite), in particular:
Global payload coverage is not possible via a single very small GEO satellite, so a compromise Ku-Band IoT mission with a smaller regional coverage area was developed.
.
The baseline SSTL platform can meet the requirements for the compromise solution and can be achieved via a low cost rideshare with the Ariane 64 HUB or Spaceflight Inc. The main platform technical developments identified in the study can also be achieved in line with a launch date of Jan 2024.
The main benefits of the baseline SSTL platform are as follows:
An ESA stand-alone technology demonstrator mission could also develop and de-risk some interesting spacecraft (e.g. Phased Arrays) and ground terminal technologies which could enable a better performance (and thus a better business case) or a lower mass (and potentially a lower cost – at least for the launch).
The Table below summarises the parameters for the baseline mission, including the capabilities and components to support the benefits described in the previous chapter.
The mission/system architecture (shown in the Figure below) was iterated throughout the study, in line with the overall concurrent mission design iterations, and including the overall lifetime of the proposed mission, from its launch and deployment, up to safe de-orbiting.
The mission architecture consists of a launch, space and a ground segment. The launch segment covers the reference launch on Ariane 64 via a HUB rideshare. The space segment comprises the VS-GEO spacecraft (which is the focus of the mission and space segment design). The ground segment consists of Users (Ground Based IoT devices), plus a Ku-Band Gateway ground station (diameter 6m) for the payload, and also an S-Band TTC ground station antenna with 5m diameter.
The Figure below summarises the project phases and milestone reviews.
The Final Report has been delivered and the project is close to completion (pending the Final Review and the Executive Summary)