CyanoSat hyperspectral imager
The three mirror telescope provides a wide field of view to collect and focus the broad range of wavelengths.
In collaboration with Australian partners, the Space Optics team has developed a compact hyperspectral imager for low-Earth orbit designed to detect blue-green algae in coastal and inland waterways. The presence of this algae can be used as an early indicator for potentially harmful algal blooms, which if not properly managed are a risk to aquatic ecosystems and cause significant economic impacts.
Measuring water quality from space is particularly challenging as imaging targets are typically small, dark, and have narrow spectral fingerprints.
Addressing these challenges, the CyanoSat payload combines a high-resolution, precision manufactured telescope with a compact filter-based spectrometer and a high signal to noise ratio in the key spectral bands needed to detect cyanobacterial algal blooms.
Additionally, the payload is designed to be lightweight and compact, making it easy to integrate into existing satellite platforms and with on-board processing capabilities.
To better understand the data requirements the team consulted closely with Earth observation colleagues and Dr Mark Matthews (CyanoLakes), who provided the team with a study that helped inform the optimum spectral range and resolution of the imager.
The Space Optics team work closely with colleagues from the Institute for Photonics and Advanced Sensing (IPAS) at the University of Adelaide, where the team’s laboratory is located.
The payload
Telescope and mirror system: To collect and focus the light the team have developed a novel off-axis three mirror anastigmatic telescope to maximise optical throughput and image quality. This fully reflective system enables a wider field of view over more traditional telescope designs and allows a broader wavelength range to be captured. The high precision machined housing, manufactured by CSIRO, enables the mirrors, surfaced by BAE Systems, to be easily aligned for maximum optical quality. This system has a 50-metre ground resolution from an altitude of approximately 600 kilometres.
Linear-variable filter: Designed and manufactured in collaboration with the Future Industries Institute at the University of South Australia, this transmissive optical filter has a resonant wavelength that varies linearly across one dimension. It is produced by precisely depositing a multilayer stack with a varying thickness, which can be tailored to capture any spectral range. By directly adhering this filter onto a camera sensor this system generates 30+ spectral bands in the visible to near-infrared.
Electronics and on-board processing: The payload electronics system is designed in-house to capture, store and process imagery from the sensor. Radiation tolerant components have been used throughout the design. Novel radiation shielding materials developed at CSIRO are also implemented into the system to increase robustness. On-board processing algorithms are used to reduce the data size before downlink. The modular design of the processing software allows it to be easily reconfigured throughout in-orbit testing.
Testing
The payload has undergone testing in the lab and on drone and high-altitude balloon platforms. Having passed pre-launch testing the CyanoSat payload is ready for its first spaceflight demonstration in mid-2023.
The flight test will see the payload fly on a Skykraft satellite as part of their rideshare offering. The team hope to conduct the following tests to measure the performance of the engineering design during this space flight:
- Communication with the payload, data download
- Monitoring house-keeping data
- Short burst image capture
- On-board processing.
The team tested early iterations of the payload on more accessible aerial platforms such as drones.
The payload components were put through a series of tests including vibration and vacuum tests.