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The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne telescope mission to search for inflationary gravitational waves from the early universe. PIPER employs two 32 × 40 arrays of superconducting transition-edge sensors, which operate at 100 mK. An open bucket Dewar of liquid helium maintains the receiver and telescope optics at 1.7 K. We describe the thermal design of the receiver and sub-Kelvin cooling with a continuous adiabatic demagnetization refrigerator (CADR). The CADR operates between 70 and 130 mK and provides ≈10 μW cooling power at 100 mK, nearly five times the loading of the two detector assemblies. We describe electronics and software to robustly control the CADR, overall CADR performance in flightlike integrated receiver testing, and practical considerations for implementation in the balloon float environment. [ABSTRACT FROM AUTHOR]

New determinations are presented of the cosmic infrared background monopole brightness in the Planck HFI bands from 100 to 857 GHz. Planck was not designed to measure the monopole component of sky brightness, so cross-correlation of the 2015 HFI maps with COBE/FIRAS data is used to recalibrate the zero level of the HFI maps. For the HFI 545 and 857 GHz maps, the brightness scale is also recalibrated. Correlation of the recalibrated HFI maps with a linear combination of Galactic H i and Hα data is used to separate the Galactic foreground emission and determine the cosmic infrared background brightness in each of the HFI bands. We obtain CIB values of 0.007 ± 0.014, 0.010 ± 0.019, 0.060 ± 0.023, 0.149 ± 0.017, 0.371 ± 0.018, and 0.576 ± 0.034 MJy sr−1 at 100, 143, 217, 353, 545, and 857 GHz, respectively. The estimated uncertainties for the 353–857 GHz bands are about 3–6 times smaller than those of previous direct CIB determinations at these frequencies. Our results are compared with integrated source brightness results from selected recent submillimeter and millimeter wavelength imaging surveys. [ABSTRACT FROM AUTHOR]

We describe the design, construction, and initial validation of the variable-delay polarization modulator (VPM) designed for the PIPER cosmic microwave background polarimeter. The VPM modulates between linear and circular polarization by introducing a variable phase delay between orthogonal linear polarizations. Each VPM has a diameter of 39 cm and is engineered to operate in a cryogenic environment (1.5 K). We describe the mechanical design and performance of the kinematic double-blade flexure and drive mechanism along with the construction of the high precision wire grid polarizers. [ABSTRACT FROM AUTHOR]

Conventional interpretation of the observed cosmic microwave background (CMB) dipole is that all of it is produced by local peculiar motions. Alternative explanations requiring part of the dipole to be primordial have received support from measurements of large-scale bulk flows. A test of the two hypotheses is whether other cosmic dipoles produced by collapsed structures later than the last scattering coincide with the CMB dipole. One background is the cosmic infrared background (CIB) whose absolute spectrum was measured to ~30% by the COBE satellite. Over the 100-500 μm wavelength range its spectral energy distribution can provide a probe of its alignment with the CMB. This is tested with the COBE FIRAS data set which is available for such a measurement because of its low noise and frequency resolution which are important for Galaxy subtraction. Although the FIRAS instrument noise is in principle low enough to determine the CIB dipole, the Galactic foreground is sufficiently close spectrally to keep the CIB dipole hidden. A similar analysis is performed with DIRBE, which-because of the limited frequency coverage-provides a poorer data set. We discuss strategies for measuring the CIB dipole with future instruments to probe the tilt and apply it to the Planck, Herschel, and the proposed Pixie missions. We demonstrate that a future FIRAS-like instrument with instrument noise a factor of ~10 lower than FIRAS would make a statistically significant measurement of the CIB dipole. We find that the Planck and Herschel data sets will not allow a robust CIB dipole measurement. The Pixie instrument promises a determination of the CIB dipole and its alignment with either the CMB dipole or the dipole galaxy acceleration vector. [ABSTRACT FROM AUTHOR]

We use absolutely calibrated data between 3 and 90 GHz from the 2006 balloon flight of the ARCADE 2 instrument, along with previous measurements at other frequencies, to constrain models of extragalactic emission. Such emission is a combination of the cosmic microwave background (CMB) monopole, Galactic foreground emission, the integrated contribution of radio emission from external galaxies, any spectral distortions present in the CMB, and any other extragalactic source. After removal of estimates of foreground emission from our own Galaxy, and an estimated contribution of external galaxies, we present fits to a combination of the flat-spectrum CMB and potential spectral distortions in the CMB. We find 2cr upper limits to CMB spectral distortions of μ < 6 × 10-4 and /Yff/ < 1 × 10-4. We also find a significant detection of a residual signal beyond that, which can be explained by the CMB plus the integrated radio emission from galaxies estimated from existing surveys. This residual signal may be due to an underestimated galactic foreground contribution, an unaccounted for contribution of a background of radio sources, or some combination of both. The residual signal is consistent with emission in the form of a power law with amplitude 18.4 ± 2.1 K at 0.31 GHz and a spectral index of -2.57 ± 0.05. [ABSTRACT FROM AUTHOR]

The ARCADE 2 instrument has measured the absolute temperature of the sky at frequencies 3, 8, 10, 30, and 90 GHz, using an open-aperture cryogenic instrument observing at balloon altitudes with no emissive windows between the beam-forming optics and the sky. An external blackbody calibrator provides an in situ reference. Systematic enors were greatly reduced by using differential radiometers and cooling all critical components to physical temperatures approximating the cosmic microwave background (CMB) temperature. A linear model is used to compare the output of each radiometer to a set of thermometers on the instrument. Small corrections are made for the residual emission from the flight train, balloon, atmosphere, and foreground Galactic emission. The ARCADE 2 data alone show an excess radio rise of 54 ± 6 mK at 3.3 GHz in addition to a CMB temperature of 2.731 ± 0.004 K. Combining the ARCADE 2 data with data from the literature shows an excess power-law spectrum ofT = 24.1 ± 2.1 (K) (v/uo)-2599°0.036 from 22 MHz to 10 GHz (v0 = 310 MHz) in addition to a CMB temperature of 2.725 ± 0.001 K. [ABSTRACT FROM AUTHOR]

We use absolutely calibrated data from the ARCADE 2 flight in 2006 July to model Galactic emission at frequencies 3, 8, and 10 GHz. The spatial structure in the data is consistent with a superposition of free-free and synchrotron emission. Emission with spatial morphology traced by the Haslam 408 MHz survey has spectral index βsynch = -2.5 ± 0.1, with free-free emission contributing 0.10 ± 0.01 of the total Galactic plane emission in the lowest ARCADE 2 band at 3.15 GHz. We estimate the total Galactic emission toward the polar caps using either a simple plane-parallel model with csc bi dependence or a model of high-latitude radio emission traced by the COBE/FIRAS map of C II emission. Both methods are consistent with a single power law over the frequency range 22 MHz to 10 GHz, with total Galactic emission toward the north polar cap TGAL = 10.12 ± 0.90 K and spectral index β -2.55 ± 0.03 at reference frequency 0.31 GHz. Emission associated with the plane-parallel structure accounts for only 30% of the observed high-latitude sky temperature, with the residual in either a Galactic halo or an isotropic extragalactic background. The well-calibrated ARCADE 2 maps provide a new test for spinning dust emission, based on the integrated intensity of emission from the Galactic plane instead of cross-correlations with the thermal dust spatial morphology. The Galactic plane intensity measured by ARCADE 2 is fainter than predicted by models without spinning dust and is consistent with spinning dust contributing 0.4 ± 0.1 of the Galactic plane emission at 23 GHz. [ABSTRACT FROM AUTHOR]

We present results of 2 mm observations of the Crab Nebula, obtained using the Goddard-IRAM Superconducting 2 Millimeter Observer (GISMO) bolometer camera on the IRAM 30 m telescope. Additional 3.3 mm observations with the MUSTANG bolometer array on the Green Bank Telescope are also presented. The integrated 2 mm flux density of the Crab Nebula provides no evidence for the emergence of a second synchrotron component that has been proposed. It is consistent with the radio power-law spectrum, extrapolated up to a break frequency of log(vb[GHz}) = 2.84±0.29 or vb = 695-336+651 GHz. The Crab Nebula is well resolved by the ~16".7 beam (FWHM) of GISMO. Comparison to radio data at comparable spatial resolution enables us to confirm significant spatial variation of the spectral index between 21 cm and 2mm. The main effect is a spectral flattening in the inner region of the Crab Nebula, correlated with the toroidal structure at the center of the nebula that is prominent in the near-JR through X-ray regime. [ABSTRACT FROM AUTHOR]

We present an update on the performance of our 2 mm bolometer camera GISMO (the Goddard IRAM2 Millimeter Observer), which is used for astronomical observations at the IRAM 30 m Telescope. The camera is optimized to efficiently observe dusty high-redshift galaxies. GISMO uses a monolithic 8 by 16 Backshort Under Grid (BUG) array with superconducting Transition Edge Sensors (TES). It serves as a testbed for our close-packed superconducting bolometer technologies and guides us in optimizing the design of future fast, low background bolometer cameras. Illustrated by astronomical observations we obtained recently, we demonstrate the scientific potential of the camera, highlighted by the detection of two high redshift galaxies. [ABSTRACT FROM AUTHOR]

We describe the electromagnetic and thermal design, performance, and fabrication for two types of radiometric-waveguide load calibrators. A simple theory is presented and used to minimize the total volume of the absorber structure. These devices have been used from room temperature to below 4 K in microwave to millimeter wavebands. The estimated precision of the calibrator is better than 1 mK absolute at temperatures near 2.7 K. [ABSTRACT FROM AUTHOR]

The calibration methods for the ARCADE II instrument are described and the accuracy estimated. The Steelcast coated aluminum cones which comprise the calibrator have a low reflection while maintaining 94% of the absorber volume within 5 mK of the base temperature (modeled). The calibrator demonstrates an absorber with the active part less than one wavelength thick and only marginally larger than the mouth of the largest horn and yet black (less than -40 dB or 0.01% reflection) over five octaves in frequency. [ABSTRACT FROM AUTHOR]

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 within a compact footprint. 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. The calibrator thermometry is stable in time over four years, with statistical uncertainty in the temperature calibration of order 2 mK near 2.7 K, limited primarily by thermal fluctuations in the liquid helium bath. Observations of the superfluid transition demonstrate that the absolute temperature scale is accurate within 0.3 mK. [ABSTRACT FROM AUTHOR]

The thermometer readout and thermal control system for the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE) experiment is described, including the design, testing, and results from the first flight of ARCADE. The noise is equivalent to about 1 Ω or 0.15 mK in a second for the RuO[SUB2] resistive thermometers at 2.7 K. The average power dissipation in each thermometer is 1 nW. The control system can take full advantage of the thermometers to maintain stable temperatures. Systematic effects are still under investigation, but the measured precision and accuracy are sufficient to allow measurement of the cosmic background spectrum. [ABSTRACT FROM AUTHOR]

We describe the design, operation, and performance of a light-weight, long-hold-time [sup 3]He cryostat used to cool the bolometric detectors of a far-infrared radiometer. A small internally pumped [sup 3]He reservoir, supported by [sup 4]He and liquid-nitrogen baths, is maintained at 0.25 K for more than a week. The cryostat has a total volume of 30 l and weights 10 kg. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]

The design and performance of a 19-GHz one-horn maser radiometer is discussed. The antenna is a lensed, conical horn with 3° angular resolution. The radiometer is stabilized by chopping against an internal cold load. A novel chopping scheme allows continual calibration of maser gain fluctuations with only a modest penalty in noise. The method of calibrating this instrument is described. The instrument has been used to map the sky with an equivalent blackbody temperature sensitivity of 1 mK per 3° × 3° resolution element. [ABSTRACT FROM AUTHOR]

Desribes the testing procedure, screening and fabrication of a low noise cryogenic preamplifier for the cosmic microwave background radiation anisotropy experiment. Construction of the test circuit; Temperature stability; Grounded input noise with preamplifier and external amplifier.