A low noise 410-495 heterodyne two tuner mixer, using submicron Nb/Al2O3/Nb tunneljunctions

A 410-495 GHz heterodyne receiver, with an array of two Nb/Al2O3/Nb tunneljunctions as mixing element is described. The noise temperature of this receiver is below 230 K (DSB) over the whole frequency range, and has lowest values of 160 K in the 435-460 GHz range. The calculated DSB mixergain over the whole frequency range varies from -11.9 plus or minus 0.6 dB to -12.6 plus or minus 0.6 dB and the mixer noise is 90 plus or minus 30 K

Detection of far-infrared rotational lines of water vapour toward W Hydrae

We report the first detection of thermal water vapour emission from a circumstellar outflow. We have observed four far-infrared rotational emission lines of water vapour and one water absorption feature toward the evolved star W Hydrae, using the Short Wavelength Spectrometer (SWS) of the Infrared Space Observatory (ISO). Three of the emission lines were observed in the instrument's Fabry-Perot mode at a resolving power lambda/Delta lambda of approximately 30 000: the 7(25) - 6(16) line at 29.84 mu m, the 4(41) - 3(12) line at 31.77 mu m, and the 4(32) - 3(03) line at 40.69 mu m One additional emission line, the 4(41) - 4(14) line at 37.98 mu m, and one absorption feature at 38.08 mu m that we attribute to a blend of the 13(13,0) - 13(12,1) and the 13(13,1) - 13(12,2) water lines were observed in grating mode at a resolving power of about 2 000. The observed emission line fluxes were 3.2 x 10(-19) 6.3 x 10(-19), 2.3 x 10(-19) and 2.8 x 10(-19) W cm(-2) respectively, and the equivalent width of the absorption feature was similar to 10 km s(-1). To within the possible errors in the flux calibration, the observed emission line fluxes can be accounted for simultaneously by a model similar to that of Chen & Neufeld (1995), given a mass-loss rate in the range (0.5 - 3) x 10(-5) M. yr(-1) This range lies at least a factor similar to 2 above an independent estimate of the mass-loss rate that may be derived from dynamical considerations, and at least a factor similar to 30 above previous estimates based upon the interpretation of CO observations

Reduction and calibration of the MIPS 70 and 160 micron detectors

The Multiband Imaging Photometer for SIRTF (MIPS) will be one of the three instruments on the Space Infrared Telescope Facility (SIRTF). MIPS will produce images at 24 (128x128 pixels), 70 (32x32 pixels), and 160 (2x20 pixels) microns using Si:As (24 micron) and Ge:Ga (70 and 160 microns) based detectors. The reduction and calibration of the Ge:Ga images present special challenges due to the nature of the bulk photoconductive detectors. The observing strategy of MIPS has been specifically designed to make the reduction and calibration of the Ge:Ga images quite robust and is different from that employed by the Infrared Space Observatory (ISO). The observations are carried out in the fast not the slow time domain, i.e. sources do not stay on the same detector pixels between exposures (3, 4, or 10 seconds). In addition, all data are taken with a high degree of redundancy and a flat field is taken every 2 minutes. The repeatability of this flat field is better than 1%. Worst case source flux repeatability of 10-15% has also been demonstrated. The general outline of the Ge:Ga data reduction and calibration will be presented. This includes continuing characterization work in the laboratory with flight-like arrays which allows for the ongoing study of the behavior of Ge:Ga detectors

Reduction and calibration of the MIPS 70 and 160 micron detectors

The Multiband Imaging Photometer for SIRTF (MIPS) will be one of the three instruments on the Space Infrared Telescope Facility (SIRTF). MIPS will produce images at 24 (128x128 pixels), 70 (32x32 pixels), and 160 (2x20 pixels) microns using Si:As (24 micron) and Ge:Ga (70 and 160 microns) based detectors. The reduction and calibration of the Ge:Ga images present special challenges due to the nature of the bulk photoconductive detectors. The observing strategy of MIPS has been specifically designed to make the reduction and calibration of the Ge:Ga images quite robust and is different from that employed by the Infrared Space Observatory (ISO). The observations are carried out in the fast not the slow time domain, i.e. sources do not stay on the same detector pixels between exposures (3, 4, or 10 seconds). In addition, all data are taken with a high degree of redundancy and a flat field is taken every 2 minutes. The repeatability of this flat field is better than 1%. Worst case source flux repeatability of 10-15% has also been demonstrated. The general outline of the Ge:Ga data reduction and calibration will be presented. This includes continuing characterization work in the laboratory with flight-like arrays which allows for the ongoing study of the behavior of Ge:Ga detectors

The guaranteed time program with the multiband imaging photometer for SIRTF (MIPS)

The GTO program for the MIPS team is concentrated in two areas. First, the evolution of planetary debris disks will be traced from their formation at less than one million years old, to the stable disks around old stars. To do so, we will make maps from 3 to 200 microns (in collaboration with the IRAC team) of regions where young stars are forming, to characterize thoroughly the circumstellar excess emission. We will include clusters representing a range of density and age. We will also observe a selection of isolated evolved stars in the MIPS photometric bands at 24, 70, and 160 microns. These observations will catalog the debris disk excesses as a function of stellar mass, age, binarity, and the presence of planetary companions. Second, we will explore the evolution of infrared galaxies and AGNs. This program has two components. In collaboration with both the IRAC and IRS teams, we will map at moderate depth 9 square degrees of sky, and in collaboration with IRAC will make deeper maps of about 2 square degrees. The latter regions have been selected to overlap with very deep xray surveys to aid in identification of AGNs and study of their evolution. We will extend the results of the deep maps by observations of 18 massive galaxy clusters in the redshift range 0.2 < z < 0.4. These clusters will image about 50 square arcmin of the background Universe, raising sources out of the confusion that will limit the sensitivity of the other deep surveys