Space debris in low Earth orbit (LEO) below 1500 km is becoming an increasing threat to spacecrafts. To manage the threat, we are developing systems to improve the ground-based tracking and imaging of space debris and satellites. We also intend to demonstrate that it is possible to launch a high-power laser that modifies the orbits of the debris. However, atmospheric turbulence makes it necessary to use adaptive optics with such systems. When engaging with objects in LEO, the objects are available only a limited amount of time. During the observation window, the object has to be acquired and performance of all adaptive optics feedback loops optimised. We have implemented a high-level adaptive optics supervision tool to automatise time-consuming tasks related to calibration and performance monitoring. This paper describes in detail the current features of our software.
As space debris in lower Earth orbits are accumulating, techniques to lower the risk of space debris collisions must be developed. Within the context of the Space Environment Research Centre (SERC), the Australian National University (ANU) is developing an adaptive optics system for tracking and pushing space debris. The strategy is to pre-condition a laser launched from a 1.8 m telescope operated by Electro Optics Systems (EOS) on Mount Stromlo, Canberra and direct it at an object to perturb its orbit. Current progress towards implementing this experiment, which will ensure automated operation between the telescope and the adaptive optics system, will be presented.
We present the status of the site-characterisation campaign at Mount Stromlo Observatory. The main goal of the project is to aid the development and operation of new adaptive optics (AO) systems for space debris tracking and pushing as well as satellite imaging. The main method we use for the characterisation is based on the SCIntillation Detection And Ranging (SCIDAR) technique. We have designed a unique version of the SCIDAR instrument: a stereo-SCIDAR system that uses a roof prism to separate beams from a double-star system to obtain two isolated pupil images on a single detector. The instrument is installed on the 1.8 m telescope of Electro-Optic Systems (EOS), sharing facilities with the adaptive optics systems we are currently building. The SCIDAR instrument will be operated intermittently, weather and availability permitting, until sufficient amount of data has been collected to characterise the site. This paper reports the current status of the project: we have recently started the commissioning phase and obtained first measurements with the instrument.
Satellite tracking and imaging is conducted by the ANU Research School of Astronomy and Astrophysics (RSAA) and Electro-Optic Systems at Mount Stromlo as part of the Space Environment Management Cooperative Research Centre to support debris tracking. To optimally design adaptive optics systems for those applications, it is important to know the atmospheric profile, i.e. how the turbulence is distributed as a function altitude. We have designed a new stereo-SCIDAR instrument1 to conduct a site characterisation campaign at Mount Stromlo site. This paper summarises our current progress: specifications, design choices and post-processing techniques. In particular, we compare two different post-processing algorithms for stereo-SCIDAR, using simulated data cubes. One of the codes is implemented by the RSAA, the other by the Centre for Advanced Instrumentation, University of Durham. The comparison shows that the current implementations of both codes produce decent results. However, we can see potential for further improvements.
Satellite tracking and imaging is conducted by the ANU Research School of Astronomy and Astrophysics and Electro-Optic Systems (EOS) at Mount Stromlo Observatory, Canberra, Australia, as part of the Space Environment Management Cooperative Research Centre (SERC) to support the development in space situational awareness. Atmospheric turbulence leads to distortions in the measured data. Adaptive optics (AO) systems counteract those distortions and improve the resolution of the tracking and imaging systems. To assist in the design of the AO systems, we need to gather information on the atmosphere at Mount Stromlo: <i>r<sub>0</sub></i>, <i>τ <sub>0</sub></i>, and the turbulence <i>C<sub>n</sub><sup>2</sup></i> profile. With the SCIntillation Detection And Ranging (SCIDAR) Technique the scintillation of two stars is measured and their autocorrelation function is computed, providing a measurement of the turbulence profile. This technique usually uses one detector recording the two images of the stars simultaneously. However, the images overlap leading to an underestimation of the <i>C<sub>n</sub><sup>2</sup></i> values. The introduction of stereo-SCIDAR1 over- comes this issue by separating the two stars and imaging them on two separate image sensors. To reduce costs, we introduce a new stereo-SCIDAR system separating the beams from the two stars, but using only one single detector. This has been shown for a Low Layer SCIDAR (LOLAS) system with wide double stars (200 arcsec). We investigate this technique by detecting the scintillation patterns of double stars with separation from 10 to 25 arcsec, allowing some flexibility in the altitude span and resolution, while retaining a simple optical setup. We selected a low noise sCMOS camera as the imager. We show the current design of this system and investigate its feasibility for further development.
So far, concepts for three dimensional biomedical imaging rely on scanning in at least one dimension. Single-shot
holography1, in contrast, stores three-dimensional information encoded in an electro-magnetic wave scattered back from
a sample in one single hologram. Single-shot holography operates with simultaneous recordings of holograms at
different wavelengths. While the lateral sample information is stored in the interference patterns of individual
holograms, the depth information is obtained from the spectral distribution at each lateral image point, similar to
Fourier-domain optical coherence tomography<sup>2</sup>. Consequently, the depth resolution of the reconstructed image is
determined by the bandwidth of the light source, so that a broadband light source is needed to obtain high depth
Additionally, the holographic material, in which the holograms are stored, restricts the useable bandwidth. A thick
photorefractive crystal can store several holograms of different wavelengths at once. As the crystal works best when
using a source with a discrete spectrum, a light source is needed that has a spectrum with well distinguishable laser
In a proof-of-principle experiment, we use colliding pulse mode-locked (CPM)<sup>3</sup> laser diodes as light sources with a
comb-like spectrum to demonstrate the concept of single-shot holography by storing multiple holograms at the same
time in a photorefractive Rh:BaTiO3 crystal.