Atmospheric modelling for NOMAD-UVIS on board the ExoMars Trace Gas Orbiter mission

The Ultraviolet and Visible Spectrometer (UVIS) instrument development process requires the construction of an atmospheric model to provide synthetic UV transmission spectra. We discuss the requirements of the model to enable observational limits to be found, and the potential for certain atmospheric parameters to be further constrained

The Restriction Principle and Commuting Families of Toeplitz Operators on the Unit Ball

On the unit ball B^n we consider the weighted Bergman spaces H_\lambda and their Toeplitz operators with bounded symbols. It is known from our previous work that if a closed subgroup H of \widetilde{\SU(n,1)} has a multiplicity-free restriction for the holomorphic discrete series of \widetilde{\SU(n,1)}, then the family of Toeplitz operators with H-invariant symbols pairwise commute. In this work we consider the case of maximal abelian subgroups of \widetilde{\SU(n,1)} and provide a detailed proof of the pairwise commutativity of the corresponding Toeplitz operators. To achieve this we explicitly develop the restriction principle for each (conjugacy class of) maximal abelian subgroup and obtain the corresponding Segal-Bargmann transform. In particular, we obtain a multiplicity one result for the restriction of the holomorphic discrete series to all maximal abelian subgroups. We also observe that the Segal-Bargman transform is (up to a unitary transformation) a convolution operator against a function that we write down explicitly for each case. This can be used to obtain the explicit simultaneous diagonalization of Toeplitz operators whose symbols are invariant by one of these maximal abelian subgroups

Monte Carlo computer simulations of Venus equilibrium and global resurfacing models

Two models have been proposed for the resurfacing history of Venus: (1) equilibrium resurfacing and (2) global resurfacing. The equilibrium model consists of two cases: in case 1, areas less than or equal to 0.03 percent of the planet are spatially randomly resurfaced at intervals of less than or greater than 150,000 yr to produce the observed spatially random distribution of impact craters and average surface age of about 500 m.y.; and in case 2, areas greater than or equal to 10 percent of the planet are resurfaced at intervals of greater than or equal to 50 m.y. The global resurfacing model proposes that the entire planet was resurfaced about 500 m.y. ago, destroying the preexisting crater population and followed by significantly reduced volcanism and tectonism. The present crater population has accumulated since then with only 4 percent of the observed craters having been embayed by more recent lavas. To test the equilibrium resurfacing model we have run several Monte Carlo computer simulations for the two proposed cases. It is shown that the equilibrium resurfacing model is not a valid model for an explanation of the observed crater population characteristics or Venus' resurfacing history. The global resurfacing model is the most likely explanation for the characteristics of Venus' cratering record. The amount of resurfacing since that event, some 500 m.y. ago, can be estimated by a different type of Monte Carolo simulation. To date, our initial simulation has only considered the easiest case to implement. In this case, the volcanic events are randomly distributed across the entire planet and, therefore, contrary to observation, the flooded craters are also randomly distributed across the planet

Radiative transfer modelling for the NOMAD-UVIS instrument on the ExoMars Trace Gas Orbiter mission

The NOMAD (Nadir and Occultation for MArs Discovery) instrument is a 3-channel (2 IR, 1 UV/Vis) spectrometer due to fly on the 2016 ExoMars Trace Gas Orbiter mission. A radiative transfer model for Mars has been developed providing synthetic spectra to simulate observations of the UVIS channel in both solar occultation and nadir viewing geometries. This will allow for the characterization and mitigation of the influence of dust on retrievals of ozone abundance

High-shock FM transmitter Final report, phase I

Electronic component testing of high-shock FM TRANSMITTER

Simulation Study of TenTen: A new Multi-TeV IACT array

TenTen is a proposed array of Imaging Atmospheric Cherenkov Telescopes (IACT) optimized for the gamma ray energy regime of 10 TeV to 100 TeV, but with a threshold of ~1 to a few TeV. It will offer a collecting area of 10 km2 above energies of 10 TeV. In the initial phase, a cell of 3 to 5 modest-sized telescopes, each with 10-30 m2 mirror area, is suggested for an Australian site. A possible expansion of the array could comprise many such cells. Here we present work on configuration and technical issues from our simulation studies of the array. Working topics include array layout, telescope size and optics, camera field of view, telescope trigger system, electronics, and site surveys.Comment: 4 pages, 7 figures, submitted to Proceedings of the ICRC 2007, pdf forma

TenTen: A New Array of Multi-TeV Imaging Cherenkov Telescopes

The exciting results from H.E.S.S. point to a new population of gamma-ray sources at energies E > 10 TeV, paving the way for future studies and new discoveries in the multi-TeV energy range. Connected with these energies is the search for sources of PeV cosmic-rays (CRs) and the study of multi-TeV gamma-ray production in a growing number of astrophysical environments. TenTen is a proposed stereoscopic array (with a suggested site in Australia) of modest-sized (10 to 30m^2) Cherenkov imaging telescopes with a wide field of view (8 to 10deg diameter) optimised for the E~10 to 100 TeV range. TenTen will achieve an effective area of ~10 km^2 at energies above 10 TeV. We outline here the motivation for TenTen and summarise key performance parameters.Comment: 4 pages, 2 figures, proceedings of the 30th ICRC, Merida, Mexico, 200

Search for bursts in air shower data

There have been reports in recent years of the possible observation of bursts in air shower data. If such events are truly of an astrophysical nature then, they represent an important new class of phemonenon since no other bursts have been observed above the MeV level. The spectra of conventional gamma ray bursts are unknown at higher energies but their observed spectra at MeV energies appear generally to exhibit a steepening in the higher MeV range and are thus unlikely to extrapolate to measurable fluxes at air shower energies. An attempt has been made to look for deviations from randomness in the arrival times of air showers above approx. 10 to the 14th power eV with a number of systems and results so far are presented here. This work will be continued for a substantial period of ime with a system capable of recording bursts with multiple events down to a spacing of 4 microns. Earlier data have also been searched for the possible association of air shower events with a glitch of the Vela pulsar