C. D. Ball

Rotational state dependence of collision induced line broadening and shift at low temperature

The dependence on rotational state of the pressure broadening and shift cross sections of the H2S–H2 and H2S–He systems is reported. The 110–101 and 211–202 transitions of H2S were studied over the temperature range 1–600 K, which includes both the low temperature quantal and the ambient semiclassical collision regimes. At low temperature collisions are mediated by the resonant formation of quasibound complexes rather than the more familiar “action-at-a-distance” mechanisms characteristic of ambient collisions. Additionally, because internal excitation of rotational states can play an important role in the formation of weakly bound complexes, the relation between the rotational energy level spacing hν, and the relative kinetic energy kT plays an important role. The low temperature regime is of interest both because of the interaction mechanism and because it is the regime characteristic of the interstellar medium. Qualitatively, the most interesting features were observed at low temperature, where signifi...

THE PRESSURE BROADENING OF SO2 BY N2, O2, HE, AND H2 BETWEEN 90 AND 500 K

Abstract The temperature dependence of the pressure broadening of four ground vibrational state rotational transitions of SO 2 have been measured. The broadening gases included N 2 , O 2 , He, and H 2 . The temperatures investigated in this work ranged from 90 to 500 K. For temperatures below 160 K, where SO 2 has negligible vapor pressure, the collisional cooling technique was used for two of the transitions. The measured broadening parameters fit well to an exponential temperature dependence over the whole range of temperatures. Room temperature values of the broadening parameter are compared with previous experimental and theoretical work.

Spatial mapping of collisionally cooled carbon monoxide molecules in a cold cell

Abstract We used a collisional cooling cell which was designed to mount directly on the second stage of a CTI-cryogenics Model 22C CRYODYNE CRYOCOOLER. The cell was maintained at approximately 14 K for all measurements reported here. The absorption path length in the cell was 4.2 cm and the window clear aperture was 1.27 cm. The position of the injector was designed to be adjustable, so we could probe the cold gas cloud from the exit plane of the injector along a vertical line to approximately 11 mm downstream from the injector. We also probed the cloud in a horizontal direction, orthogonal to the previous direction. Our beam is imaged to a spot diameter of approximately 1 mm in the center of the cell. Gas temperatures as low as 24 K were measured approximately 11 mm from the nozzle and temperatures of approximately 40 K were measured close to the exit plane of the nozzle. Carbon monoxide was used for all measurements.

The CubeSat Radiometer Radio Frequency Interference Technology Validation (CubeRRT) mission

The CubeSat Radiometer Radio Frequency Interference Technology Validation (CubeRRT) mission is developing a 6U CubeSat system to demonstrate radio frequency interference (RFI) detection and mitigation technologies for future microwave radiometer remote sensing missions. CubeRRT will perform observations of Earth brightness temperatures from 6-40 GHz using a 1 GHz bandwidth tuned channel, and will demonstrate on-board real-time RFI processing. The system is currently under development, with launch readiness expected in 2018 followed by a one year period of on-orbit operations. Project plans and status are reported in this paper.

Performance characteristics of a low-temperature cell for collisional cooling experiments

We fabricated and tested a low temperature cell which is mounted directly on the second stage of a CTI-Cryogenics Model 22C CRYODYNE CRYOCOOLER. The vacuum system consists of a room temperature vacuum shroud, a radiation shield maintained at 77K and the cell which is mounted directly to the second stage of the cryocooler. The ultimate cell temperature is 12.4 Kelvin, and the low temperature limit increases at a rate of 5.6 Kelvin/Watt. We achieve a cell temperature of 22 Kelvin under typical experimental conditions of approximately 29 milli Torr helium, slow flowing gas, and a heated injector. The absorption path length of the cell is 3.35 cm, and the window clear aperture is 1.27 cm. We preformed a series of experiments in which we determined the translational temperatures of vibration- rotation transitions in the band of CO for different cell temperatures. The results of our tests are discussed in this paper.

Development of the cubesat radiometer radio frequency interference technology validation (cuberrt) system

The CubeSat Radiometer Radio Frequency Interference Technology Validation (CubeRRT) mission is developing a 6U CubeSat system to demonstrate radio frequency interference (RFI) detection and filtering technologies for future microwave radiometer remote sensing missions. CubeRRT will perform observations of Earth brightness temperatures from 6–40 GHz using a 1 GHz bandwidth tuned channel and will demonstrate on-board real-time RFIS processing. The system is currently under development, with an expected launch date in mid-2018 followed by a one year period of on-orbit operations. Development of the CubeRRT spacecraft, radiometer instrument, and concepts of operation are described in this paper.