Christoffer Korvald

An open-source scheduler for small satellites

The limited power generation capability of a small satellite (e.g., a CubeSat) requires robust scheduling. A scheduling approach for small satellites which considers subsystem inter-dependency (where co-operation is required, desirable or prohibited), operational requirements and ground communication windows is presented. The paper considers what the optimal way of scheduled tasks for autonomous operation (required for scheduling when not in communication with ground controllers and desirable at all times during the mission) is. It compares a genetic algorithm-based approach, an exhaustive search-based approach and a heuristic-based approach. Performance maximization is considered (in light of both decision-making time and reducing activity time).

Sensor and computing resource management for a small satellite

A small satellite in a low-Earth orbit (e.g., approximately a 300 to 400 km altitude) has an orbital velocity in the range of 8.5 km/s and completes an orbit approximately every 90 minutes. For a satellite with minimal attitude control, this presents a significant challenge in obtaining multiple images of a target region. Presuming an inclination in the range of 50 to 65 degrees, a limited number of opportunities to image a given target or communicate with a given ground station are available, over the course of a 24-hour period. For imaging needs (where solar illumination is required), the number of opportunities is further reduced. Given these short windows of opportunity for imaging, data transfer, and sending commands, scheduling must be optimized. In addition to the high-level scheduling performed for spacecraft operations, payload-level scheduling is also required. The mission requires that images be post-processed to maximize spatial resolution and minimize data transfer (through removing overlapping regions). The payload unit includes GPS and inertial measurement unit (IMU) hardware to aid in image alignment for the aforementioned. The payload scheduler must, thus, split its energy and computing-cycle budgets between determining an imaging sequence (required to capture the highly-overlapping data required for super-resolution and adjacent areas required for mosaicking), processing the imagery (to perform the super-resolution and mosaicking) and preparing the data for transmission (compressing it, etc.). This paper presents an approach for satellite control, scheduling and operations that allows the cameras, GPS and IMU to be used in conjunction to acquire higher-resolution imagery of a target region.

Model-based software engineering for an imaging CubeSat and its extrapolation to other missions

Small satellites with their limited computational capabilities require that software engineering techniques promote efficient use of spacecraft resources. A model-driven approach to software engineering is an excellent solution to this resource maximization challenge as it facilitates visualization of the key solution processes and data elements.

Toward requirements engineering of cyber-physical systems: Modeling CubeSat

The OpenOrbiter CubeSat Development Initiative is working to build a small spacecraft system using open source software and open hardware principles. The important design considerations for the CubeSat include availability and performance. The essential contribution of this paper is the requirement elicitation and specification of system-wide qualities such as availability, performance, and security using quality attribute scenarios. The effect of using the quality-based scenarios is that it allows more rigorous treatment of non-functional requirements and hence proper selection of an architecture modeling to satisfy these requirements.

Impact of a revised standard for best practices for academic, governmental and industrial ground station scheduling and communications design

As launches and satellites lower in overall cost, the variety and purpose of the data collected continues to evolve. This evolution requires a revised set of standards for best practices with regard to academic, governmental and industrial communication and scheduling design. With deliberate consideration into communication and scheduling design, throughput of data passed via the ever more crowded and noisy limited-bandwidth channels can be improved. This study outlines how implementing a revised standard with regard to ground station scheduling and communication impact the expectation for throughput from the satellite itself.