Nanosatellite scheduling using a dictionary module and a ‘useful trick’ with coded unsigned integers

Schedulers for small spacecraft must satisfy the dual requirement of generating very efficient schedules while concurrently minimizing the resources required to create the schedule. This paper proposes a technique for searching for tasks that can be utilized to fill particular schedule locations. This approach is based on a modular system for storing important variables. This modular system has three important variables: t₀, x₀ and y₀. The variable y is latitude and x is longitude. Time variable t is an integer and each unit represents a time quantum. They are related to each other by three functions F_t, F_x, and F_y. These functions are derived from a space time function where x₀ and y₀ are the normalized ground trace. These three variables can define a prospective instance of any task on an Earth-orbiting spacecraft. Similarly, this same approach could be used for planetary missions by making the ground trace references in relation to the local body. This approach is based on a ´useful trick´ that can be performed with integers that facilitates the encoding of conditional statements using these three variables. This trick helps define the life cycle of a task. This approach can also, if needed, be expanded to allow the incorporation of other variables. This paper considers the limits of using integers in this way. It presents and considers several example problems and demonstrates the efficacy of using this algorithm to generate a solution.