We propose observations of the molecular gas distribution during the era of reionization. At z ∼ 6 to 8, 12 CO(J = 1 − 0) line intensity results in a mean brightness temperature of about 0.5 µK with rms fluctuations of 0.1 µK at 1 to 10 Mpc spatial scales, corresponding to 30 arcminute angular scales. This intensity fluctuations can be mapped with an interferometer, similar to existing and planned 21-cm background experiments, but operating at ∼ 12 to 17 GHz. We discuss the feasibility of detecting the cross-correlation between HI and CO molecular gas since such a cross-correlation has the advantage that it will be independent of systematics and most foregrounds in each of the 21-cm and CO(1 − 0) line experiments. Additional instruments tuned to higher-order transitions of the CO molecule or an instrument operating with high spectral resolution at mmwavelengths targeting 158 µm CII could further improve the reionization studies with molecular gas. The combined 21-cm and CO line observations has the potential to establish the relative distribution of gas in the inter-galactic medium and molecular gas that are clumped in individual first-light galaxies that are closely connected to the formation of massive stars in these galaxies.

We describe the design and calibration of an external cryogenic blackbody calibrator used for the first two flights of the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) instrument. The calibrator consists of a microwave absorber weakly coupled to a superfluid liquid helium bath. Half-wave corrugations viewed 30• off axis reduce the return loss below -35 dB. Ruthenium oxide resistive thermometers embedded within the absorber monitor the temperature across the face of the calibrator. The thermal calibration transfers the calibration of a reference thermometer to the flight thermometers using the flight thermometer readout system. Data taken near the superfluid transition in 8 independent calibrations 4 years apart agree within 0.3 mK, providing an independent verification of the thermometer calibration at temperatures near that of the cosmic microwave background.

We present new high-resolution measurements of transient time-domain photoconductivity in ErAs:InGaAs superlattice nanocomposites intended for THz photoconductive switches and photomixers using a pure optical pump-probe method. We developed a model, using separate photocarrier trapping, recombination, and thermal reactivation processes, which very accurately fits the measurements. The measured material structures all exhibit a slow secondary decay process, which is attributed to thermal reactivation of the trapped carriers, either into the conduction band, or into high-energy defect states. We examined the influence of superlattice structure, dopants, DC bias, and temperature. Analysis shows that all of the THz energy produced by the photocarrier trapping and decay processes are at frequencies less than 1 THz, while the reactivation process only serves to create a large portion of the bias power dissipated. Energy higher than 1 THz must be created by a fast generation process or band-filling saturation. This allows pulsed THz generation even from a long-lifetime material. Pure optical pump-probe measurements are necessary to expose slow material processes, and eliminate the influence of electrical terminals and THz antennas. These measurements and modeling of THz photoconductive devices are necessary in order to optimize the output spectrum and power.

A balloon borne stabilized platform has been developed for a remotely operated altitude-azimuth pointing of a millimeter wave telescope system. A modeling and controller design of the azimuth point system of the platform is presented. Simulation results show that the system is capable of continuous operation with pointing rms to better than 0.01 deg. Ground testing results show continuous operation with pointing rms to better than 0.02 deg; while results of the first flight from the National Scientific Balloon Facility (NSBF) at Palestine, Texas show pointing rms better than 0.02 deg.

We report on laboratory studies of the effectiveness of directed energy planetary defense as a part of the DE-STAR (Directed Energy System for Targeting of Asteroids and exploRation) program. DE-STAR [1][5][6] and DE-STARLITE [2][5][6] are directed energy "stand-off" and "stand-on" programs, respectively. These systems consist of a modular array of kilowatt-class lasers powered by photovoltaics, and are capable of heating a spot on the surface of an asteroid to the point of vaporization. Mass ejection, as a plume of evaporated material, creates a reactionary thrust capable of diverting the asteroid's orbit. In a series of papers, we have developed a theoretical basis and described numerical simulations for determining the thrust produced by material evaporating from the surface of an asteroid [1][2][3][4][5][6]. In the DE-STAR concept, the asteroid itself is used as the deflection "propellant". This study presents results of experiments designed to measure the thrust created by evaporation from a laser directed energy spot. We constructed a vacuum chamber to simulate space conditions, and installed a torsion balance that holds an "asteroid" sample. The sample is illuminated with a fiber array laser with flux levels up to 60 MW/m 2 which allows us to simulate a mission level flux but on a small scale. We use a separate laser as well as a position sensitive centroid detector to readout the angular motion of the torsion balance and can thus determine the thrust. We compare the measured thrust to the models. Our theoretical models indicate a coupling coefficient well in excess of 100 µN/Woptical, though we assume a more conservative value of 80 µN/Woptical and then degrade this with an optical "encircled energy" efficiency of 0.75 to 60 µN/Woptical in our deflection modeling. Our measurements discussed here yield about 45 µN/Wabsorbed as a reasonable lower limit to the thrust per optical watt absorbed.