Showing papers by "Mark Halpern published in 1996"

Anisotropy in the Microwave Sky: Results from the First Flight of BAM

Abstract: Results are reported from the first flight of a new balloon-borne instrument, BAM (Balloon-borne Anisotropy Measurement), designed to search for cosmic microwave background (CMB) anisotropy. The instrument uses a cryogenic differential Fourier transform spectrometer to obtain data in five spectral channels whose central frequencies lie in the range 3.7 cm^{-1} to 8.5 cm^{-1}. The spectrometer is coupled to an off-axis prime focus telescope; the combination yields difference spectra of two regions on the sky defined by 0\fdg 7 FWHM beams separated by 3\fdg 6. Single differences obtained at ten sky positions show statistically significant fluctuations. Assuming Gaussian correlated anisotropy, for the band average 3.1 cm^{-1} to 9.2 cm^{-1}, one finds $\Delta T/T = 3.1^{+3.1}_{1.1}\times 10^{-5}$ (90% confidence interval) for a correlation angle of 1\fdg 2. This corresponds to $Q_{flat} = 35.9^{17.7}_{6.3} \mu K$ (1\sigma).

A system for grabbing integrated video frames remotely

Abstract: A system for grabbing integrated video frames produced by a remote camera is described. As part of the pointed platform in a balloon‐borne experiment, we use a video charge‐coupled‐device camera to obtain wide field star images. To obtain images with a sufficient signal‐to‐noise ratio, integration times of up to 1 s are required. In applications where the frame grabber and camera are physically close to each other, timing the frame grabber trigger is straightforward; however, there are several advantages to locating the frame grabber not on the balloon payload. As a result commands issued simultaneously to the frame grabber on the ground and the camera on the balloon can be delayed relative to each other, resulting in failure to acquire an image. We have developed a system where, at the end of an integration, a tone is injected into the video field preceding the transmission of the integrated frame; the tone is used on the ground by a decoder circuit to control the frame grabber acquisition of the integrated frame. The system has operated successfully in the flight of a stratospheric balloon‐borne telescope.