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WG3K > ANS 13.03.25 04:05l 31 Lines 4656 Bytes #162 (0) @ AMSAT
BID : ANS068.2
Read: GUEST
Subj: GOLF-TEE Advances: Flight Software and Bus Status
Path: IZ3LSV<ED1ZAC<CX2SA<N3HYM<WG3K
Sent: 250313/0015Z 14949@WG3K.#SMD.MD.USA.NOAM LinBPQ6.0.24
Burns Fisher, WB1FJ recently presented a review of the progress being made on the GOLF-TEE flight software, and an overview of the satellite electrical busses and telemetry.
This next generation of GOLF satellites (Greater Orbit – Larger Footprint) marks a new era of communications satellites. The GOLF series of satellites requires technologies that are new to AMSATs CubeSat program. The first satellite of this ambitious effort is called GOLF-TEE for Technology Exploration Environment. As an experimental mission, GOLF-TEE is designed to fly in an readily available and low cost low-earth orbit. Its purpose is to test technologies that will be used in later GOLF satellites.
Figure 1 shows a 3D printed model of the circuit boards for the GOLF-TEE satellite
built by Tom Karnauskas, N0UW, AMSAT mechanical engineer.
Fisher showed the audience a new 3D printed model of GOLF-TEE and its circuit board mockups to be secured on aluminum rails. GOLF Project Engineers are optimizing placement of the circuit boards so a model of each board is a big help. They are confronting the challenges that satellite designers face when trying to fit stacks of circuit boards, batteries, complex control systems, and experimental payloads inside a 10cm x 10cm x 30cm spaceframe that is the core of a three-unit CubeSat. He explained that the four fold-out solar panels are expected to generate about 36 Watts of power in full-sun. Fisher commented, “Thats a surprising amount of power.”
But, before GOLF-TEE is ready to fly, several earth-bound versions of the satellite are used by AMSAT engineers. A “flatsat” is a generic term describing the first attempt at interconnecting the circuit boards to be used in the satellite. The components are spread out on a table for easier access to subsystems. At this point, the circuit boards may not even look like what the final items will look like. The flatsat is used for initial testing and development of the circuits as well as the software that runs and communicates with the systems.
Figure 2 shows a device under test in the WB1FJ shack. It illustrates why the term flatsat
is used to describe how prototypes are initially assembled for development and testing.
The project uses an AMSAT Linear Transponder Module (LTM) for command/control, telemetry, and a V/U linear transponder as well as a newly designed Radiation-Tolerant processor (the RT-IHU). The satellite will utilize a real-time operating system controlling three microprocessors. He said, “Processor coordination is new to GOLF. It keeps watch over processing monitoring for failures. It copes with failures by switching processors.”
GOLF-TEE uses a number of different electrical busses, including I2c and SPI. The purpose of any bus is to communicate among different electrical units while reducing wiring complexity,
Fisher described the eight software programs, also called tasks, that the Real-Time operating system manages:: Downlink Control; Telemetry Collection; Diagnostic Console; Receiver/Transmitter Control; Commanding; Experiment Control; Processor Coordination; and CAN Support.
Figure 3 identifies the circuit boards that must communicate with each other
via different electrical busses and their stacking arrangement.
Fishers work includes tests of the CAN bus and the Central Interface Unit connecting various subsystems. The CAN bus is a controller area network that is a vehicle bus standard designed to enable efficient communication primarily between electronic control units. The CAN bus is new to the AMSAT CubeSat program.
GOLF-TEE will carry a Vanderbilt University a RadFx (Radiation Effects) experiment using I2C data communication format. Vanderbilt Universitys Institute for Space and Defense Electronics analyzes radiation-hardened electronics, develops test methods and plans for assuring radiation hardness, and develops solutions to system-specific problems related to radiation effects.
An upcoming feature of a future GOLF satellite will be the ability to comply with NASAs Orbital Debris and Collision Avoidance Requirements for satellites flying at higher orbits. This means carrying not only an attitude detection and control system but a possible propulsion system needed to de-orbit the satellite at the end of its useful life.
Burns Fisher credited technical contributions to the program by Chris Thompson, VE2TCP, Rich Gopstein, KD2CQ, and Bill Schell, W2WZ. Fisher is a life member of AMSAT and the volunteer lead flight software developer for GOLF Satellites.
[ANS thanks Burns Fisher, WB1FJ, AMSAT GOLF Lead Flight Software Developer for the above information.]
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