Tunable Antenna Coupled Intersubband Terahertz Detector

We report on the development of a tunable antenna coupled intersubband terahertz (TACIT) detector based on GaAs/AlGaAs two dimensional electron gas. A successful device design and micro-fabrication process have been developed which maintain the high mobility (1.1x106 cm2/V-s at 10K) of a 2DEG channel in the presence of a highly conducting backgate. Gate voltage-controlled device resistance and direct THz sensing has been observed. The goal is to operate as a nearly quantum noise limited heterodyne sensor suitable for passively-cooled space platforms

Model of Dust Thermal Emission of Comet 67p-Churyumov-Gerasimenko for the Rosetta-MIRO Instrument

The ESA's Rosetta spacecraft will arrive at comet 67P/Churyumov-Gerasimenko in 2014. The study of gas and dust emission is primary objective of several instruments on the Rosetta spacecraft, including the Microwave Instrument for the Rosetta Orbiter (MIRO). We developed a model of dust thermal emission to estimate the detectability of dust in the vicinity of the nucleus with MIRO. Our model computes the power received by the MIRO antenna in limb viewing as a function of the geometry of the observations and the physical properties of the grains. We show that detection in the millimeter and submillimeter channels can be achieved near perihelion

Compact Receiver Front Ends for Submillimeter-Wave Applications

The current generation of submillimeter-wave instruments is relatively mass and power-hungry. The receiver front ends (RFEs) of a submillimeter instrument form the heart of the instrument, and any mass reduction achieved in this subsystem is propagated through the instrument. In the current implementation, the RFE consists of different blocks for the mixer and LO circuits. The motivation for this work is to reduce the mass of the RFE by integrating the mixer and LO circuits in one waveguide block. The mixer and its associated LO chips will all be packaged in a single waveguide package. This will reduce the mass of the RFE and also provide a number of other advantages. By bringing the mixer and LO circuits close together, losses in the waveguide will be reduced. Moreover, the compact nature of the block will allow for better thermal control of the block, which is important in order to reduce gain fluctuations. A single waveguide block with a 600- GHz RFE functionality (based on a subharmonically pumped Schottky diode pair) has been demonstrated. The block is about 3x3x3 cubic centimeters. The block combines the mixer and multiplier chip in a single package. 3D electromagnetic simulations were carried out to design the waveguide circuit around the mixer and multiplier chip. The circuit is optimized to provide maximum output power and maximum bandwidth. An integrated submillimeter front end featuring a 520-600-GHz sub-harmonic mixer and a 260-300-GHz frequency tripler in a single cavity was tested. Both devices used GaAs MMIC membrane planar Schottky diode technology. The sub-harmonic mixer/tripler circuit has been tested using conventional metal-machined blocks. Measurement results on the metal block give best DSB (double sideband) mixer noise temperature of 2,360 K and conversion losses of 7.7 dB at 520 GHz. The LO input power required to pump the integrated tripler/sub-harmonic mixer is between 30 and 50 mW

Implications of the Ammonia Distribution on Jupiter from 1 to 100 Bars as Measured by the Juno Microwave Radiometer

The latitude-altitude map of ammonia mixing ratio shows an ammonia-rich zone at 0-5degN, with mixing ratios of 320-340 ppm, extending from 40-60 bars up to the ammonia cloud base at 0.7 bars. Ammonia-poor air occupies a belt from 5-20degN. We argue that downdrafts as well as updrafts are needed in the 0-5degN zone to balance the upward ammonia flux. Outside the 0-20degN region, the belt-zone signature is weaker. At latitudes out to +/-40deg, there is an ammonia-rich layer from cloud base down to 2 bars which we argue is caused by falling precipitation. Below, there is an ammonia-poor layer with a minimum at 6 bars. Unanswered questions include how the ammonia-poor layer is maintained, why the belt-zone structure is barely evident in the ammonia distribution outside 0-20degN, and how the internal heat is transported through the ammonia-poor layer to the ammonia cloud base

Implications of the ammonia distribution on Jupiter from 1 to 100 bars as measured by the Juno microwave radiometer

The latitude‐altitude map of ammonia mixing ratio shows an ammonia‐rich zone at 0–5°N, with mixing ratios of 320–340 ppm, extending from 40–60 bars up to the ammonia cloud base at 0.7 bars. Ammonia‐poor air occupies a belt from 5–20°N. We argue that downdrafts as well as updrafts are needed in the 0–5°N zone to balance the upward ammonia flux. Outside the 0–20°N region, the belt‐zone signature is weaker. At latitudes out to ±40°, there is an ammonia‐rich layer from cloud base down to 2 bars that we argue is caused by falling precipitation. Below, there is an ammonia‐poor layer with a minimum at 6 bars. Unanswered questions include how the ammonia‐poor layer is maintained, why the belt‐zone structure is barely evident in the ammonia distribution outside 0–20°N, and how the internal heat is transported through the ammonia‐poor layer to the ammonia cloud base.Key PointsThe altitude‐latitude map of Jupiter’s ammonia reveals unexpected evidence of large‐scale circulation down at least to the 50‐bar levelA narrow equatorial band is the only region where ammonia‐rich air from below the 50‐bar level can reach the ammonia cloud at 0.7 barsAt higher latitudes the ammonia‐rich air appears to be blocked by a layer of ammonia‐poor air between 3 and 15 barsPlain Language SummaryJupiter is a fluid planet. It has no solid continents to stabilize the weather. Scientists have wondered what the weather is like below the clouds because it might explain why storms last for decades or hundreds of years on Jupiter. The Juno spacecraft is the first chance we have had to take a look beneath the clouds, and this is the first analysis of the Juno data. The surprise is that, deep down, Jupiter’s weather looks a lot like Earth’s, with ammonia gas taking the place of water vapor. There is a band of high humidity at the equator and bands of low humidity on either side of the equator, like Earth’s tropical and subtropical bands. What is different is that the bands go much deeper than anyone expected and this is all taking place on a planet without an ocean or a solid surface.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/138332/1/grl56217_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/138332/2/grl56217.pd

Implications of the ammonia distribution on Jupiter from 1 to 100 bars as measured by the Juno microwave radiometer

The latitude-altitude map of ammonia mixing ratio shows an ammonia-rich zone at 0–5°N, with mixing ratios of 320–340 ppm, extending from 40–60 bars up to the ammonia cloud base at 0.7 bars. Ammonia-poor air occupies a belt from 5–20°N. We argue that downdrafts as well as updrafts are needed in the 0–5°N zone to balance the upward ammonia flux. Outside the 0–20°N region, the belt-zone signature is weaker. At latitudes out to ±40°, there is an ammonia-rich layer from cloud base down to 2 bars that we argue is caused by falling precipitation. Below, there is an ammonia-poor layer with a minimum at 6 bars. Unanswered questions include how the ammonia-poor layer is maintained, why the belt-zone structure is barely evident in the ammonia distribution outside 0–20°N, and how the internal heat is transported through the ammonia-poor layer to the ammonia cloud base

ESA Rosetta Spacecraft Mission to Comet Churyumov-Gerasimenko: The Orbiter

No abstract availabl

A submillimeter sounder for the Titan Saturn System Mission (TSSM)

International audienc