Search Results

The current status of III-V semiconductor diode lasers emitting between 1 -5 μm wavelengths to be used as light sources for absorption spectroscopy is reviewed. The emission wavelength of the laser is chosen to coincide with the primary absorption line of a molecule or one of its many overtones. The lasers, with a single longitudinal mode emission, are wavelength tuned over several angstroms by modulating the drive current of the device. This sweeping of the wavelength leads to the nomenclature tunable diode laser or TDL. Single mode distributed feedback (DFB) strained layer InGaAs(P) lasers grown on InP substrates with emission wavelengths from 1.2 to 2.06 μm have been developed at JPL, and several devices will be used for planetary atmospheric studies for the first time.

In recent years, several different technologies have been considered for use in environmental monitoring and control of spacecraft habitat. These technologies have included monitoring for both water and air. This paper will discuss construction of a trade space for environmental monitoring technologies. Previous trade space metric approaches are reviewed and a new approach is outlined. Trade space considerations include the usual mass, power and volume, along with sensitivity, accuracy, speed of response, frequency of measurement and ease of use. These considerations will be discussed in the context of Constellation program vehicles. In addition to a new approach for trade space construction, this paper will briefly discuss the application of this trade space to a selection of technologies taken from NASA programs, ESA programs, COTS technologies and DoD programs.

The French-Indian MEGHA-TROPIQUES satellite is devoted to the atmospheric research. Data collected by the satellite will improve our knowledge on the water cycle contribution to the climate dynamic in the tropical atmosphere and our understanding of the processes linked to the tropical convection. The payload is made of MADRAS (developed by CNES and ISRO) and of two instruments provided by CNES: SAPHIR and SCARAB. The paper presents: the thermal control design of the two CNES instruments SAPHIR and SCARAB, taking into account the mechanical and scientific constraints. This design is based on a passive thermal control, on uses of heating power for cold cases or safe mode. This thermal design is today analyzed and the main results will be shown; the validation logic is now defined and instrument thermal tests are in preparation. These instrument thermal tests will be done in the second part of 2008.

The exploration of Mars is a major thrust of NASA. Some of the important goals of this exploration are the search for life; understanding the planet's evolution by in-situ and remote scientific measurements; developing an inventory of useful resources, including accessible water; and sample return as a precursor to human exploration. One of the key challenges of Mars's exploration hard-ware--- rovers, landers, probes, and science instruments -- is to be able to survive the planet's harsh environment on and below surface. This paper discusses the thermal challenges posed by relatively large temperature variations, analyses and experimental work done at JPL to address these challenges.

The Netlander mission aims to deploying on the surface of Mars a network of 4 landers, which will perform simultaneously measurements in order to study the internal structure of Mars, its sub-surface and its atmosphere. This paper describes the phase B thermal control concept of the Netlander Surface Module, taking into account various thermal environments from the cruise to Mars phase until the landing and the one Martian year phase on the Mars surface. The paper focuses on two specific thermal tests. The first one is a thermal conductivity measurement of three pre-selected insulation materials in a 6 - 10 hPa CO2 environment, and the second one is a performance test of a Loop Heat Pipe designed to comply the Netlander Surface Module needs. This paper is mainly derived from the report referenced ref. 1.

The INTERnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) is an ESA observatory scientific satellite which was successfully launched on the 17th of October 2002. The payload consists in four instruments : an optical camera (OMC), a X-ray monitor (XRM), an imager (IBIS) and a spectrometer (SPI). The spectrometer (20 keV-8 MeV energy range, 2.3 m high, 1.1 m diameter, around 1300 kg) has been supplied by CNES where this instrument has been managed, assembled and tested before delivery to ESA for satellite level activities. This paper describes the spectrometer flight model thermal design achieved thanks to the different international partners, gives and overview of the cryostat used to cool down the detection plane and exposes the thermal validation plan used at instrument level (thermal mathematical model and thermal test philosophy, cryostat thermal validation). We then focus on in-flight performances and compare them to expected ones.

ChemCam is one of the 10 instrument suites on the Mars Science Laboratory, a martian rover being built by Jet Propulsion Laboratory, for the next NASA mission to Mars (MSL 2009). ChemCam is an instrument package consisting of two remote sensing instruments: a Laser-Induced Breakdown Spectrometer (LIBS) and a Remote Micro-Imager (RMI). LIBS provides elemental compositions of rocks and soils, while the RMI places the LIBS analyses in their geomorphologic context. Both instruments rely on an autofocus capability to precisely focus on the chosen target, located at distances from the rover comprised between 1 and 9 m for LIBS, and 2 m and infinity for RMI. ChemCam will help determine which samples, within the vicinity of the MSL rover, are of sufficient interest to use the contact and in-situ instruments for further characterization.

A microhygrometer has been developed at JPL's Microdevices Laboratory based on the principle of dewpoint/frostpoint detection. The surface acoustic wave device used in this instrument is approximately two orders of magnitude more sensitive to condensation than the optical sensor used in chilled-mirror hygrometers. In tests in the laboratory and on the NASA DC8, the SAW hygrometer has demonstrated more than an order of magnitude faster response than commercial chilled-mirror hygrometers, while showing comparable accuracy under steady-state conditions. Current development efforts are directed toward miniaturization and optimization of the microhygrometer electronics for flight validation experiments on a small radiosonde balloon.

The Viking project is managed by the Viking project office at Langley Research Center for the National Aeronautics and Space Administration. Two Viking spacecraft will be individually launched on a new Titan IIIE/Centaur D-1T launch vehicle in August 1975. The method for the establishment of spacecraft sine vibration test levels prior to availability of any Titan IIIE/Centaur D-1T flight data by use of both computer simulations and data from previous Titan and Atlas Centaur vehicles is described. The specification level is compared with actual flight data obtained from a proof flight launch of the Titan IIIE/Centaur D-1T and a Viking dynamic simulator in January 1974. An objective of the proof flight launch was to obtain estimates of the flight loads and environments. The criteria used to minimize the structural weight that would result from an unmodified application of a sine test environment are described.

One startling realization that's come from NASA's explorations of the satellites of Jupiter and Saturn is that the so-called “habitable zone” around our Sun may not be restricted to Earth's vicinity. The Galileo mission found conditions that might support life on two Jovian moons-Europa & Callisto. This raises the possibility of habitable zones elsewhere near the outer planets. Consideration of human missions beyond Mars, likely to occur sometime beyond the year 2040, exceeds the horizon of even the most advanced planning activities within NASA. During the next 25 to 30 years, robotic spacecraft are envisioned to explore several moons of outer planets, especially Europa and Titan. Since Callisto lies well outside Jupiter's radiation belt, and there is evidence of water ice there is a compelling rationale to send human explorers to that Jovian moon.

Although important efforts are actually devoted to improve Si-Ge materials, their thermoelectric energy conversion efficiency remains relatively low and the adimensional ZT value does not exceed 1. Higher values can be obtained by investigating new materials. A search for new high temperature thermoelectric materials identified a certain number of compounds between transition metals and bismuth, antimony and germanium as potential candidates. Results of the preliminary synthesis of samples by a variety of techniques (Bridgman, mechanical alloying…) are presented as well as some electrical measurements. Some compounds showed interesting properties and need to be investigated in more details.

A simple Loop Heat Pipe (LHP) with a single evaporator and condenser was tested and modeled with two different working fluids: ammonia and propylene. While ammonia exhibits many desirable heat transfer characteristics, its freezing point is too high to prevent freezing in the condenser lines during a safing mode on a satellite platform. Consequently, propylene makes a good compromise since it has a lower freezing point and relatively good heat transfer properties. The performance of the LHP with ammonia was characterized by a series of tests with heat loads of 20 to 800 watts placed on the evaporator. With the LHP filled with propylene, it was tested with heat loads of 20 to 200 watts to the evaporator. The sink temperatures on the condenser ranged from −10°C to 20°C. The constant conductance performance of the LHP was 170 W/K with ammonia and 44 W/K with propylene. Steady state performance data of the LHP was used to validate a nodal network model of the device.

An Electronic Nose is being developed at JPL and Caltech for use in environmental monitoring in the International Space Station. The Electronic Nose (ENose) is an array of 32 polymer film conductometric sensors; the pattern of response may be deconvoluted to identify contaminants in the environment. An engineering test model of the ENose was used to monitor the air of the Early Human Test experiment at Johnson Space Center for 49 days. Examination of the data recorded by the ENose shows that major excursions in the resistance recorded in the sensor array may be correlated with events recorded in the Test Logs of the Test Chamber.

1 This paper describes the conception and development status of a mini pump for two phases cooling loops. This pump is able to transport heat until 500 watts with a very low mass, low power consumption, and for a long lifetime (up to15 years)

A miniature quadrupole mass spectrometer array has been designed and tested. It consists of 16 rods in a 4 x 4 array. The ionizer is of a miniature Nier-type, and the detector is a channel-type multiplier. The demonstrated mass range is 1-300 u, and the resolution of the system is 0.1 -0.5 u (FWHM), or m/Δm = 600. The present sensitivity is measured and calculated to be approximately 1 x 1012 counts/torr-sec. Applications to NASA missions will be outlined, along with military and commercial uses.

The Mars Pathfinder (MPF) Spacecraft, scheduled for a December 1996 launch to Mars, uses a mechanically pumped loop to transfer dissipated heat from the insulated lander electronics to an external radiator. This paper discusses the tradeoffs performed before choosing a mechanical pumped loop as the thermal control system for MPF. It describes the analysis, tradeoffs, design, and predicted performance of this system. The various development tests performed are discussed, along with the current status of this cooling system. Finally, some thoughts on the development of mechanically pumped loops for future spacecraft are presented.

Rovers will play a vital role in upcoming Mars missions by enabling science activities at a wide variety of locations even kilometers away from the landing site. On-going technology development efforts at the Jet Propulsion Laboratory include the Long Range Science Rover Task which is prototyping and demonstrating rover technology capable of traversing several kilometers over the Martian surface carrying out a wide variety of science activities. This paper discusses the operational requirements for Mars science rovers and a current prototype Mars rover called Rocky 7.

The effects of both the cosmic ray heavy ion exposures and the intense trapped electron exposures are examined with respect to impact on cellular system survival on exterior spacecraft surfaces as well as at interior (shielded) locations for a sample mission to Jupiter’s moons. Radiation transport through shield materials and subsequent exposures are calculated with the established Langley heavy ion and electron deterministic codes. In addition to assessing fractional DNA single and double strand breaks, a variety of cell types are examined that have greatly differing radio-sensitivities. Finally, implications as to shield requirements for controlled biological experiments are discussed.

The Mars Pathfinder spacecraft which will be launched in December 1996 features an active cooling system for controlling the temperature of the spacecraft. This will be the first time that such a mechanical pump cooling system is used on an interplanetary or long duration flight (over two weeks) in space. The major element of the cooling system is the Integrated Pump Assembly (IPA). It uses centrifugal pumps to circulate liquid freon to transfer heat from spacecraft electronics to an external radiator. The IPA consists of redundant pumps, motor control electronics, thermal control valves, check valves, and an accumulator. The design and flight implementation of this pump assembly were accomplished in less than two years. This paper describes the design, fabrication, assembly, and testing of the IPA.

The effect of changes in the carrier concentration and mobility for heavily doped n-type SiGe on the electrical power factor has been investigated. It has been shown that power factors of 37-40 μV/cm-K2 can be achieved with carrier concentrations of 2.0 - 2.5 × 1020 cm-3 and mobilities of 38-40 cm2/V-sec. Many samples with suitable carrier concentration do not have high mobilities and some rationale for this behavior is presented. Initial results are presented on fabrication of n-type samples from ultra-fine powders. The emphasis in this work is to achieve thermal conductivity reductions by adding inert particles to scatter mid-frequency phonons.