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Stevan Spremo is the project manager of COTSAT-1, or Cost Optimized Test of Spacecraft Avionics and Technologies. The ongoing development project aims to build a fully functional spacecraft for $500,000 in parts and$2 million labor. The prototype is the first of what could be a series of rapidly produced, low-cost flight vehicles.

#### NASA Tech Briefs: What is COTSAT-1?

Stevan Spremo: COTSAT-1 was a successful attempt to make a low cost modular spacecraft. The COTSAT-1 architecture allows for a lower-cost, more serviceable spacecraft that can be reconfigured in a rapid prototype environment. We have unique ways to take it apart, put it back together, and iterate on the design. Many other spacecraft are very customized, one-off systems that you can’t really access and change that much.

#### NTB: What are the parts of COTSAT-1?

Spremo: The parts of the COTSAT-1 system include solar arrays; an avionics bus "can," which is a pressurized volume; electrical power management system; PC104 computer; communications systems; and a guidance navigation and control system (including reaction wheels, torque coils, star trackers, and inertial measurement unit). There is room to add a propulsion system in future generations.

#### NTB: What makes the spacecraft modular?

Spremo: Modularity is present in all subsystems, including the software. The Linux-based platform was coded in modules that can be added and deleted from the system with ease, without impacting the overall development. [Linux] also allows for parallel programming efforts on modules for separate subsystems, which saves costs compared to other spacecraft industry approaches to software.

Hardware modularity is present from how the solar array structure is assembled, to how the avionics are accessed and serviced. Accessing the avionics is designed to be more like servicing an aircraft engine — a timeline of hours — rather than traditional approaches of assembling and dissembling a spacecraft, which could take days to months of coordinated effort.

There is a standard approach for accessing all hardware in the system. Quick-disconnect cabling and clamps allow the avionics tray to be slipped out in one craning lift or horizontal slide. The internal avionics tray is layered in three tiers, enabling a fast swap of internal subcomponents if necessary. An entire power system swap could happen in minutes. It is possible to assemble and disassemble the entire space vehicle system in a single day if all subsystem assemblies are available at the same time.