Advanced Instrumentation

Space-based instrumentation, Ground-based space surveillance/tracking – optical telescope, Ground-based space surveillance/tracking – passive radar, and Advanced Imaging and Remote Sensing Systems.
Advanced Instrumentation
Credit: NASA

Space-based instrumentation:

Conducting space-based research requires space-based instrumentation. UNSW Canberra has a heritage of world-class diagnostics for high-speed and/or harsh environments, and in particular has a proven track record in maintaining, ruggedising and flying a diode-laser sensor on the SCRAMSPACE hypersonic flight experiment in 2013. In general, UNSW Canberra is well placed to establish leadership in space-based instrumentation development. In particular, further development of the diode laser sensor for space-based measurements of atmospheric greenhouse gas distributions has commenced and will be demonstrated in orbit.

As UNSW Canberra’s in-orbit capabilities progress to satellite formations, development of the laser sensor will be extended to enable distributed sensor measurements across formations, significantly enhancing the extent and nature of the measurements made. This in turn provides a pathway to development of other examples of distributed sensors to take advantage of the opportunities afforded by low-cost satellite formations.

In parallel, other advanced instruments will be pursued, in particular the application of electron beam spectroscopy to in-orbit density measurements. This will be tested in the laboratory thermal vacuum chamber environment to determine the altitude limits of the approach, which offers the possibility to directly determine rather than infer local density. If feasible, electron beam spectroscopy would be a candidate for future flights.

Ground-based space surveillance/tracking – optical telescope:

UNSW Canberra hosts the second Southern Hemisphere telescope commissioned so far in the USAF Academy led global optical telescope space surveillance/tracking research network, the Falcon Telescope Network. Our research telescopes can detect 1m objects in geostationary orbit and track 1cm objects in Low Earth Orbit. UNSW Canberra is extending the capabilities of the telescope to multiple modalities (wavelength of measurement, mitigation of sky background for daytime operation and atmospheric turbulence through adaptive optics, and observe signal oscillations characteristic of space-object rotations) and will provide leadership in developments required for tasking and handover of space objects from one telescope to the next across the network. This in turn presents the opportunity for UNSW Canberra to play a role in the broader challenge of tasking and handing over from one type of ground-based sensor to the next in order to obtain information about space objects of complexity greater than one sensor alone can provide – an issue of growing strategic importance and opportunity for Australia. UNSW Canberra’s Falcon telescope will also play a complementary role to local laser tracking activities, and by close-coupling it to our flight experiments we will be able to make an important contribution to development of optical telescope capability for space situational awareness, and responsibly monitor the wellbeing of our own satellites.

An application of the ground-based surveillance research includes the measurement of the time varying history of the measured intensity, using multiple wavelengths, of images of space objects too small and/or far away to resolve. These histories are known as light curves, are a function of the orientation, shape, and reflective properties of the space object, and provide important input to SSA.

Ground-based space surveillance/tracking – passive radar:

UNSW Canberra is also performing the systematic stepping-stone development of passive radar for space surveillance, based on detection of satellite-generated radio signals scattered from space objects. Space objects have very low and predictable dynamics with very low target density, allowing the use of radar techniques which would fail in more general circumstances. There are a large number of radio emitters in space, including GPS (and GNSS more broadly), communication, radar and TV satellites. A passive radar system employing these emitters would work in all weather, could simultaneously track every object above the horizon in an affordable system, and provide target tracking at the wavelength (centimeter) level. In other words, it would be potentially game-changing for SSA. The key driver for passive radar performance is radiated power.

Notwithstanding an assumption that the total power radiated by space-based emitters will grow with time, collecting sufficient energy from each observation is challenging. This is because the already weak signal from a satellite is scattered from a small object, and then suffers of order 1000km of free space spreading loss prior to collection at the Earth’s surface. Therefore an affordable means to collect sufficient energy is needed. Options are to increase the aperture in area, to collect signals from more (or higher power) transmitters, or to increase the integration time. Research and experimentation is necessary to determine the appropriate trade between each means of increasing the energy collected from the target, and it is plausible that the best system will depend on the size of the object to be observed. UNSW Canberra, with the assistance of CSIRO, has begun the task of exploring the feasibility of the Australian SKA Pathfinder radio telescope network for such a purpose. This work is revolutionary in the field, but is incremental in extending on well understood scientific phenomena and sound engineering developed for other fields.

Advanced Imaging and Remote Sensing Systems:

Traditional optical and microwave sensors map the distribution of energy spatially across a scene or area of interest. However, the electromagnetic field carries a wealth of information that can be extracted from its spectral, polarization, and coherence properties that are often neglected. The ability to measure these classes of information from space will provide new reconnaissance and SSA capabilities beyond what is possible with traditional imaging. Prof. Scott Tyo recently joined UNSW Canberra from the College of Optical Sciences at the University of Arizona where he directed the advanced sensing laboratory. Through understanding of the full range of processes including electromagnetic interaction with targets, propagation of signals through the atmosphere, transduction of the electromagnetic information through the sensor, and final exploitation of the data. This end-to-end, physics based understanding helps to develop specialized sensors that are extremely well-suited to particular remote sensing missions. Active research is being conducted at UNSW Canberra in polarimetry (active and passive), spectral imagery, infrared imagery, and coherence manipulation that has the potential to impact applications such as ISR, SSA, and atmospheric remote sensing from space.