Research Byte
Published in the RSAA Lunations
Vol1 Issue10 1–30 November 2020
Seeking a change from the usual challenges of sky-subtraction and emission-line identification, I recently swapped Integral Field Spectroscopy for satellite based Hyper-Spectral Imaging. It turns out that, even with an abundance of photons, remote sensing of the aquatic environment is still complicated by background light contamination with surface reflections (or glint) from the sun creating a highly variable signal, confusing surface detections and masking underwater structures.
Remote sensing observations are already widely used by land-based industry and civil programs. It is of course widely exploited in Australia for critical uses such as crop health and water management for agriculture, mineralogical survey support for targeting in situ fieldwork, etc. Indeed I’m also exploring ways to use infrared systems to assist with bushfire hazard minimisation (see our ANU press release from back in March). However, in the marine environment extensive parallel applications exist for remote water quality assessment in domestic use, reef health (long-term tourism support), or the fisheries and aquaculture industry. For many of these civil applications the nuisance parameters, those that complicate the delivery of value-add data products to the end user, are associated with attributes such as underwater visibility and basic classification of the nature and variation in subsurface structure. These latter properties are of course fundamental to many Defence applications for denied area surveillance, rapid analysis of beach approaches, and increasingly, logistical support for disaster relief in rapidly unfolding turbulent environments.
With this in mind we’ve partnered with the Defence Materials Technology Centre (DMTC), CSIRO, and local satellite service provider Skykraft to deliver the CHICO project (Cubesat Hyperspectral Imager for the Coastal Ocean), under the DMTC High Altitude Sensor Systems (HASS) program. While initially envisaged for deployment with a UAV or High Altitude Pseudo-Satellite (HAPS), the Australia Space Agency came into being during (protracted) contract negotiations and so the program's focus shifted somewhat towards design of a compact system suitable for Low Earth Orbit operations from a 12U CubeSat.
The baseline design is for an optical (400-800 nm) long-slit spectrograph, with the translation of the slit across the ground (at a terrifying speed, we now realise of course) providing the 3D data cube as the satellite passes over the region of interest. While initially a “visible light” system, my current obsession with the Leonardo SAPHIRA eAPD detectors means we’re already making mental modifications to the system to push out into the Shortwave Infrared (SWIR) region, which is critical for the bushfire program (OzFuel) and some other exciting industry applications.
A critical part of both the CHICO and OzFuel missions, as well as our astronomy mission planned for the International Space Station (I’ll volunteer Joice to write about the Emu space telescope next month) is the detector control system (Rosella -more info here) currently being developed by the electronics group.
Australia’s reliance on satellite data to provide critical and timely information for less accessible parts of the Earth is growing. The bespoke elements of the CHICO mission provide the first steps in a sovereign Australian program to address the challenges of remote sensing in the marine environment for civil, industrial, research and defence applications. It also ensure our wider instrumentation programs can stay relevant and continue to grow in these challenging times.
Rob Sharp
