The Low Cost EO Developments Project, supported by CEOI, has enabled SSTL to accelerate key developments of the SSTL-1000 high resolution optical satellite. The work conducted has included progressing the design and engineering of the low cost optical Precision Imager payload and an innovative high-throughput Payload Data Handling Unit (PDHU), and the development of an Inter-Satellite Link (ISL) allowing the IP for these systems to remain with SSTL. The project has given SSTL the opportunity to ensure the design of SSTL-1000 platform is of sufficient maturity to take maximum advantage of near term Earth observation constellation opportunities which will bring benefit to both SSTL and the wider UK space industry, particularly in the Earth observation technology and applications sectors.
Left : Primary mirror mounted for testing; Centre: PDHU EM Unit; Right: ISL antenna under test in SSTL anechoic chamber
The main activity has been to mature the design of the SSTL-1000 optical payload, the Precision Imager, to TRL 4. The Precision Imager is a Ritchey-Chretien design instrument providing 0.5 m GSD panchromatic and 1 m GSD multispectral imagery as well as 0.5 m GSD HD video from a reference orbital altitude of 450 km. Activities have included manufacture of a primary mirror breadboard, which have incorporated development of SSTL’s highly accurate mirror measurements processes, manufacture of the Engineering Models (EM) of the payload electronics and a newly designed focus mechanism, and production and testing of the anamorphic lens assembly.
The PDHU is responsible for recording the vast amount of data generated by the imaging payloads, managing and storing that data, and making the data available for high speed downlink. This will greatly increase the performance of SSTL’s satellite platforms. The requirement for the PDHU has been driven by the high rate at which the precision imager acquires data. However, this sub-system is relevant not only to the SSTL-1000 platform but to numerous future SSTL EO mission developments.
The PDHU is a modular card based system which can be configured to support numerous payload configurations and storage requirements. The main processing element is a Xilinx Virtex-7 FPGA which is capable of multiple simultaneous operations and contains vast resources for processing payload data. This project focused on progressing the PDHU design and building the first EM unit with key activities including the design of the power card and backplane and manufacture of EM hardware. In parallel additional developments have included the firmware (VHDL) and software, initially generating test software but progressing to core flight software over the duration of the project.
Based on SSTL’s S-band Telemetry and Telecommand (TT&C) system the Inter Satellite Link (ISL) will provide the SSTL-1000 with the capability to communicate with, and task, other satellites in a constellation; a key market differentiator and a requirement for one particular near term commercial constellation opportunity. The ISL focused activities have resulted in the development two new antenna products, enabled the next generation TT&C module to be manufactured and tested and the subsequent ISL transmit only and receive only avionics designs to be proof tested.
This project has resulted in a significant step forward in low cost optical space capability for the UK’s space industry. Addressing a well-defined near term customer need, the Technology Readiness Level of the Precision Imager, PDHU and ISL developments have been raised to prepare for multiple commercial large constellation mission opportunities and a variety of other future missions.