CROSS

A new generation star tracker

We're happy to announce that CROSS has placed 1st in the Research Innovation Prize!

Thank you to everyone who has supported us along the way!

CROSS is a star tracker project led by the School of Aerospace, Mechanical, and Mechatronic Engineering in the Faculty of Engineering at the University of Sydney, in collaboration with the Australian Research Council Training Centre for CubeSats, UAVs & Their Applications (CUAVA). The project is led by Joshua Critchley-Marrows, under the supervision of Dr. Xiaofeng Wu, and Professor Iver Cairns, director of CUAVA. CROSS is an Australian-made and Australian-owned space system capability, built to serve the emerging Australian space sector. We would be pleased to receive interest from both Australian and International industry - please get in touch by the email address below.

Why CROSS?

Advanced Attitude Determination

CROSS is a high-precision attitude determination device used in satellite pointing systems. Attitude determination is achieved by comparison of the known positions of stars to an image’s calculated positions.

Designed for Small Satellites

This system will provide high-precision attitude determination to pico- and micro-satellites, such as the CubeSat and up to the 50 kg classes. The majority of star trackers available today are designed for large satellites and hence have significantly larger mass, volume, and cost. 

Developing Capability

The project will develop a competitive and accessible star tracker platform to grow Australia’s space capability through Sydney University researchers and students.

Features

Multiple Sensors

Multi-axis star tracking with sensor fusion for enhanced accuracy and operability. 

Customisable Layout

Designed to allow sensors to be assigned mission-specific positions.

Novel Software

Novel algorithms for increased accuracy and performance as well as robustness in multiple scenarios.

Small Form Factor

Designed to be compatible for use within the CubeSat template.

Wide FOV

Application of wide field of view to allow for lower cost optics without decreasing performance.

Low Cost

Prioritising easy access for small businesses and research institutions.

Research Papers

Investigation into Integrated Attitude Determination in High-Precision Cubesats
International Astronautical Congress 2017
Abstract CubeSats are becoming increasingly popular devices for security encryption applications, where a high pointing accuracy is sometimes required. Star trackers are currently the best tool available to achieve highly accurate attitude determination. Although, currently highly precise forms of these devices are both large and expensive, where the algorithms are intensive on processing and data storage. Such characteristics prove difficult for application to small satellite devices, such as CubeSats. Using an integrated network of sensors and actuators, which may include a more rudimentary star tracker, could avoid such issues developing. Use of magnetometers, horizon sensors and sun sensors are more fitted for CubeSat applications, but do not achieve the accuracy star trackers are capable of. This paper seeks to investigate this integrated actuator and sensor design to improve the accuracy of CubeSats, whilst avoiding the issues discussed previously. The possible use of a smartphone as a star tracker is also investigated, utilising the cellular devices’ economies of scale, processing power and small size. This work is done with applications to quantum key distributions between satellites, and more specifically CubeSats. The project involves development of 3 unit CubeSat’s with a pointing accuracy of at least 0.01°. For such a mission, a highly-accurate attitude determination and control system is required, with attitude measurements well below the desired pointing budget.

Joshua Critchley-Marrows

Investigations into the Effects and Mitigation Strategies for Stray-Light Pollution in Wide-Field-Of-View Star Trackers 
Australian Space Research Conference 2018
Abstract Previous work has indicated that the use of Commercial-Off-The-Shelf (COTS) smartphone cameras in satellite Star Trackers is promising, due to their low cost, mass, and volume, limited power consumption, and high radiometric and spatial resolution. This paper presents an investigation of the effect of stray light on a novel Star Tracker comprising a Wide-Field-of-View (WFOV), low cost, COTS camera system. The blinding angle from the camera boresight to centre of Sun, Earth and Moon is estimated via laboratory and ground experiments. Both hardware and software solutions to optimising these angles are briefly investigated, such as baffling, introducing multiple orthogonal cameras, and correction algorithms. The experimental results show the effect of stray light to be very significant, rendering the system inoperable if no mitigation strategies are implemented.

Dominic Albertson

Assessing the viability of a wide field of view based stellar gyroscope
Australian Space Research Conference 2018
Abstract A stellar gyroscope system is proposed, designed, and its accuracy evaluated. The stellar gyroscope operates by imaging over long exposure times and measuring the position and size of smeared stars to determine a spin axis and slew rate. The benefits of using a stellar gyroscope include a lack of sensor bias and a lack of need for a separate gyroscope system. An experimental apparatus was designed and tested, and images and real gyroscope data were captured for comparison. The developed system was not accurate enough to be used solely in an attitude determination and control system; however, it may be used for secondary verification, sensor bias reduction, or as a redundancy measure in low-cost satellites.

Julian Guinane

Investigation into Star Tracker Algorithms using Smartphones with Application to High-Precision Pointing CubeSats
Transactions of the Japan Society for Aeronautical and Space Sciences, Aerospace Technology 2019
Abstract For all common satellite attitude determination sensors, star trackers provide the most accurate measurement. However, these devices can be both large and expensive, and for some CubeSat applications it would not be suitable. Star trackers have in the past been successfully made for CubeSats. This paper investigates star tracker algorithms, implemented with a smartphone, so it may be used for testing attitude determination on a CubeSat. By testing through a proposed implementation, star centroids should be found by the moment method, stars should be identified by planar triangles, and QUEST should be used for attitude estimation. Smeared star images should be avoided and blurred images provide greater accuracy. Using these techniques, a star tracker using a smartphone may be constructed for attitude determination testing and software development, applied in the lost-in-space situation. This may be applied to QKD CubeSats, which require an attitude precision below 0.01°.

Joshua Critchley-Marrows

A Calibration Technique with Kalman Filtering for Multiple Star Tracker Wide Field of View Camera Sensors
International Symposium on Space Technology and Science 2019
Abstract This paper presents a new calibration methodology for in-orbit estimation of optical parameters for star trackers. The novel approach is specific for a wide field of view star tracker. The work is based from the CROSS project of the University of Sydney, which involves development of a multi-sensor, wide field of view star tracker designed for small satellites. The effect of distortion is especially pronounced for a wide field of view camera. Errors in the camera frame leads to reduced accuracies of the determined attitude. Two types of distortion are identified, focal plane and radial distortion. This leads to five parameters that must be estimated in-orbit, either by method of least squares or by an extended Kalman filter. In the proposed approach, a combination of both techniques isapplied, implementing three types of algorithms for calibration. The use of these considered parametersisjustified by use of a real night sky image, captured with a smartphone camera with a horizontal field of view of 64.2°.The proposed model is then simulated for a horizontal field of view of 60°, considering varying initial offsets and a noise of 0.05 px. The model successfully converges after approximately 50 iterations.

Joshua Critchley-Marrows

Development of a Low-Cost Testing Methodology for Star Trackers
Australian Space Research Conference 2019
Abstract This paper describes a method for accuracy validation of a star tracker optical system using night sky testing. Data from the IAU2000A earth rotation model was used to correct for Earth precession and nutation effects. This method was tested by analysing data captured using a stationary smartphone camera over a period of 75 minutes. Applying these corrections resulted in measured accuracies of 8.903’ in boresight accuracy and 7.007’ in cross-boresight accuracy. This represented a notable improvement over the accuracy measured without using the IAU2000A model, which found a boresight accuracy of 14.621’ and a crossboresight accuracy of 11.998’.

Benjamin Jarvis

Implementation of a WFOV Star Tracker in CubeSat and Small Satellite Attitude Determination Systems
Comittee on Space Research Scientific Assembly 2021 (Unpublished - Abstract Accepted)
Abstract This paper analyses the differences between wide and near field of view star tracker systems and suggests methods to address the various challenges which arise, including exposure to stray light and lens distortion. By addressing the requirements of a star tracker system incorporating the WFOV concept, a CubeSat orientated design for the system is proposed. An overview of components which would support such a system is presented, including optical, computing, and mechanical considerations. Finally, a concept of operations for the system is explored, including the operating modes which enable its functionality and account for its limitations.

Matthew Suntup

The Team

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Joshua Critchley-Marrows

Project Lead

Dr. Xiaofeng Wu

Engineering Supervisor

Prof. Iver Cairns

Physics Supervisor

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Dominic Albertson

Student Researcher

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Julian Guinane

Student Researcher

Benjamin Jarvis

Student Researcher

Matthew Suntup

Student Researcher

School of Aerospace, Mechanical and Mechatronic Engineering

University of Sydney
NSW, Australia

Contact

Please email us if you are interested in finding out more about the project or collaborating.

team@CrossStarTracker.com

The ARC Industrial Transformation Training Centre for CubeSats, UAVs, and Their Applications (CUAVA) received Australian Government funding through the Australian Research Council Industrial Transformation Research Program.