Testing the GP-B telescope readout electronics on a flight quality telescope

Integrated photodiodes and silicon JFET preamps are used for the optical readout of the Gravity Probe B cryogenic star tracking telescope. The heated circuit assembly is mounted on a thermal isolator so that it can be heated to around 80 K while the telescope remains at its operating temperature of 2.8 K. We present test results of the readout with a flight quality telescope

Modelling X-ray scattering factors from fluids of some fluorinated molecules and related compounds

Abstract: There is current interest, both for basic science and technological applications, in fluorocarbons such as CF4 and the related molecules. Here we first report a Hartree-Fock calculation of the ground-state electron density in the octahedral molecule SF6 using the experimentally determined bond length. From this density, the number of electrons lying inside a sphere of radius r, denoted by Q(r), centred on the S nucleus has been extracted. The X-ray scattering factor f(k) is then modelled using Q(r) and compared with f(k) for the isoelectronic united atom ytterbium. The molecule CF4, together with its isoelectronic partners PF3, CrF2 and AsF, is again compared with regard to f(k) with the united atom Mo. Finally, interest in modelling PbF is pointed out, in relation to the quantum-chemical theory already available