Elozor Plotke, LinQuest Corporation; Peter C. Lai, LinQuest Corporation; Yingwai (Andy) Chan, United States Space Force SSC; Roberta M. Ewart, United States Space Force SSC; Kyle Miller, Ball Aerospace; Jacob Griesbach, Ball Aerospace
Keywords: Medium Accuracy Star Tracker (MAST), star tracker, space domain awareness (SDA), sensor, in-space developmental test, in-space processing algorithms
Abstract:
Star observation based attitude determination systems have gained in popularity for modern spacecraft in the last two decades. As such, star trackers are deemed as standard sensors on current space vehicles. Numerous research has been devoted to the star tracker hardware development as well as the use of star trackers. The principle of star tracker relies on the star measurements through a set of optical lenses then projected on its focal plane assembly (FPA), which is typically 512 x 512, or 1024 x 1024 pixel charge-coupled device (CCD) or complementary metaloxidesemiconductor (CMOS). The star measurement on FPA is then compared to a predetermined star catalog to obtain attitude solution.
In the past decade, Space Domain Awareness (SDA) has become an increasingly important topic due to the concerns of safety of operating satellites in a proliferated Low Earth Orbit (pLEO) and Geosynchronous Earth Orbit (GEO) congested environments as well as potential adversary events to the satellites. Similar to star tracker functionality, SDA also utilizes optical sensors to detect and track objects in space against a predetermined catalog. Therefore, the star tracker is well suited for SDA functionality. The full-frame measurement on star trackers FPA may be made available in a continuous video mode output for SDA processed either on the ground or in space. The dual-use sensor combining star tracker and SDA functionalities has advantage of lower size, weight, power, and cost (SWaP-C) as compared to two dedicated star tracker and SDA sensors, respectively.
The United States Space Force (USSF) Space and Missile Systems Center (SMC) requires that Department of Defense (DoD) satellites use star trackers for safe navigation and attitude control. For defense industry base (DIB) consideration, additional measure of maintaining at least one domestic source of vendor with product competitive in the global market is implemented. Therefore, a dual-use star tracker is being developed accordingly. This star tracker is capable of producing up to 10 Hz autonomous attitude solution at moderate accuracy as well as full-frame video for SDA processing. In the first phase of the development, SDA will be processed on the ground, while in the second phase the onboard SDA processing will be enhanced.
The purpose of testing this star tracker in space is to verify performance and functional requirements of both star tracker and SDA sensor functionalities in a relevant space environment in order to accelerate the Technical Readiness Level (TRL) of this product from TRL-5 to TRL-7 or above. Star tracker performance test, functional demonstration, and analyses include Switch ON, On-Orbit Calibration, Nominal Attitude Tracking, Maneuver Attitude Tracking, Sun Exclusion Angle Verification, Earth Blinding, Moon Blinding, Lost-in-Space Recovery, and Test Data Analyses.
The on-orbit SDA tests and demonstrations will be nominally performed with the star tracker attached to the spacecraft. The SDA processing will utilize star trackers 10 Hz full frame video output. At the initial phase, the video data will be downlinked from the spacecraft in real-time to the ground for SDA post-processing. In the following phase in-space, SDA processing will be performed as a demonstration of next generation in-space computing technology. SDA Sensor performance test and function demonstration, and analyses test events include Sun Exclusion Angle Verification, Earth Blinding, and Laser, Dazzle, and Moon Blinding.
Additionally, post-processing data of the above on-orbit tests and demonstrations along with subsequent analyses will serve as model validation and improve the fidelity of a ground-based simulation representing the star tracker and SDA sensor functionality and performance.
In this paper, the development and requirements of this dual-use star tracker, its proposed test plan and scenarios, along with the resulting technology maturity and enabling future capability will be discussed.
Date of Conference: September 14-17, 2021
Track: Optical Systems & Instrumentation