1. Flight Software for KySat-1
Samuel Hishmeh, Tyler Doering, Daniel Erb, Jason Bratcher, Nate Rhodes, James E. Lumpp Jr.
Space Systems Laboratory, University of Kentucky
Abstract
Telemetry
Hardware Software Integration
A critical part of the design process for KySat-1 was the hardware and software integration. This procedure melded the software flow of the design to the combination of custom and off the shelf hardware systems.
The Kentucky Space consortium is a collaborative effort of public and private partners throughout the state of Kentucky focused on small satellite development and access to space for small payloads. In 2006, the consortium was formed under the leadership of Kentucky Science and Technology Corporation (KSTC), a nonprofit corporation committed to the advancement of science, technology and innovative economic development in Kentucky. Kentucky Space’s goal is to establish a competitive space program in Kentucky by developing the infrastructure and expertise needed to sustain a program that will be beneficial to the state.
KySat-1 has the ability to record various telemetry points concerning operation of the satellite. This telemetry data can then be downloaded from the spacecraft and used as diagnostic, informational or educational tools. The software has the ability to gather these data sets on command or autonomously.
Design Philosophy
The flight software of KySat-1 has been designed to be modular, reliable and reusable.
Modularity is achieved by designing subsystem specific code independently followed by an integration period. This allows the software to be developed in stages, thus resulting in shorter development times.
Reliability is achieved through a stringent design process followed by first extensively testing each sub system and then extensive testing of the integrated hardware and software systems.
Reusability is achieved through the modular design approach which allows the reliable code to be leveraged for other purposes, thus reducing future development time.
Figure 5: Hardware block diagram for KySat-1.
Figure 1: Control Flow of KySat-1 Flight Software
Fault Tolerance
Communication Systems
One of the major fault tolerance measures of the spacecraft are the various modes of operation. Entry into each mode is governed by a set of specific criteria designed to assure maximum reliability of the spacecraft. For instance if communication from the ground stations has not occurred within a predetermined number of days the satellite will reset itself to known, well defined configuration in an attempt to re-establish communication.
Figure 3: Software abstraction layers
KySat-1 employs both UHF/VHF and S-Band communication systems while allowing users to interact with the spacecraft by exploiting several avenues.
In addition to these principles, the flight software for KySat-1 leveraged off the shelf software packages as much as possible. Among these are Salvo, the Real Time Operating system (RTOS) from Pumpkin Inc in addition to the file system libraries purchased from HCC-Embedded.
Development Infrastructure
The flight software of KySat-1 was developed in a highly structured environment. The development process was designed to achieve maximum productivity independent of the number of developers. This was achieved through the usage of collaboration tools such as revision control (SVN), documentation database (wiki) and the aforementioned design philosophies. In order to expedite development time, software was developed on representative hardware provided by the same company (Pumpkin Inc) as the flight hardware.
Figure 4: Representative (left) and flight (right) computers for KySat-1.
Figure 2: Communication channels for KySat-1
Figure 6: Operating modes for KySat-1