Space instrumentation

Abstract:

Several post-common envelope binaries have slightly increasing, decreasing or oscillating orbital periods. One of several possible explanations is light travel-time changes, caused by the binary centre-of-mass being perturbed by the gravitational pull of a third body. Further studies are necessary because it is not clear how a third body could have survived subdwarf progenitor mass-loss at the tip of the Red Giant Branch, or formed subsequently. Thirty-nine primary eclipse times for V470 Cam were secured with the Philip Wetton Telescope during the period 2016 November 25thto 2017 January 27th. Available eclipse timings suggest a brown dwarf tertiary having a mass of at least 0.0236(40) M, an elliptical orbit with an eccentricity of 0.376(98) and an orbital period of 11.77(67) years about the binary centre-of-mass. The mass and orbit suggest a hybrid formation, in which some ejected material from the subdwarf progenitor was accreted on to a precursor tertiary component, although additional observations would be needed to confirm this interpretation and investigate other possible origins for the binary orbital period change.

Abstract:

Measurements of the light scattering behaviour of the regoliths of airless bodies via remote sensing techniques in the Solar System, across wavelengths from the visible to the far infrared, are essential in understanding their surface properties. A key parameter is knowledge of the angular behaviour of scattered light, usually represented mathematically by a phase function. The phase function is believed to be dependent on many factors including the following: surface composition, surface roughness across all length scales, and the wavelength of radiation. Although there have been many phase function measurements of regolith analog materials across visible wavelengths, there have been no equivalent measurements made in the thermal infrared (TIR). This may have been due to a lack of TIR instruments as part of planetary remote sensing payloads. However, since the launch of Diviner to the Moon in 2009, OSIRIS-Rex to the asteroid Bennu in 2016, and the planned launch of BepiColombo to Mercury in 2018, there is now a large quantity of TIR remote sensing data that need to be interpreted. It is therefore important to extend laboratory phase function measurements to the TIR. This paper describes the design, build, calibration, and initial measurements from a new laboratory instrument that is able to make phase function measurements of analog planetary regoliths across wavelengths from the visible to the TIR.