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  • 1
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    Media Calibration in the Deep Space Network: A Status Report (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: A new media calibration system (MCS) has been implemented at the Goldstone complex of the DSN (Deep Space Network). It is intended to calibrate the delay of radio signals imposed by the neutral atmosphere. The system provides periodic measurements of both the static dry and fluctuating wet components of this delay. In particular, the system will calibrate the fluctuations in line of sight path delay due to atmospheric water vapor that we believe will dominate the error budget for several radio science and radio astronomy experiments. We have compared two of these media calibration systems with a connected element interferometer on a 21 km baseline. In this report we describe a total of 30 observations in which a radio source was tracked for an hour or more and the delay residuals then calibrated using the MCS. The accuracy of the comparison appears to be limited by systematic errors in the interferometer, which are under investigation. However, our results do indicate that the MCS can meet or exceed the two-way Allan standard deviation specification of 1.5 x 10( exp -15) on time scales of 2,000 - 10,000 sec, as required by the Cassini GWE (Gravitational Wave Experiment) for two way Doppler tracking.
    Keywords: Geophysics
    Type: International VLBI Service for Geodesy and Astrometry General Meeting Proceeding; 194-198; NASA/CP-2002-210002
    Format: text
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  • 2
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    Calibration of Atmospherically Induced Delay Fluctuations Due to Water Vapor (2000)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: We have completed a new generation of water vapor radiometers (WVR), the A- series, in order to support radio science experiments with the Cassini spacecraft. These new instruments sense three frequencies in the vicinity of the 22 GHz emission line of atmospheric water vapor within a 1 degree beamwidth from a clear aperture antenna that is co-pointed with the radio telescope down to 10 degree elevation. The radiometer electronics features almost an order of magnitude improvement in temperature stability compared with earlier WVR designs. For many radio science experiments, the error budget is likely to be dominated by path delay fluctuations due to variable atmospheric water vapor along the line-of-sight to the spacecraft. In order to demonstrate the performance of these new WVRs we are attempting to calibrate the delay fluctuations as seen by a radio interferometer operating over a 21 km baseline with a WVR near each antenna. The characteristics of these new WVRs will be described and the results of our preliminary analysis will be presented indicating an accuracy of 0.2 to 0.5 mm in tracking path delay fluctuations over time scales of 10 to 10,000 seconds.
    Keywords: Meteorology and Climatology
    Type: International VLBI Service for Geodesy and Astrometry: 2000 General Meeting Proceedings; 274-279; NASA/CP-2000-209893
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  • 3
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    Extending the ICRF to Higher Radio Frequencies: 24 and 43 GHz Astrometry (2004)
    In:  CASI
    Details
    Publication Date: 2018-06-06
    Description: We present imaging results and source structure analysis of extragalactic radio sources observed using the Very Long Baseline Array (VLBA) at 24 GHz and 43 GHz as part of an ongoing NASA, USNO, NRAO and Bordeaux Observatory collaboration to extend the International Celestial Reference Frame (ICRF) to higher radio frequencies. The K/Q-band image database now includes images of 108 sources at 43 GHz (Q-band) and images of 230 sources at 24 GHz (K-band). Preliminary analysis of the observations taken to date shows that the sources are generally more compact as one goes from the ICRF frequency of 8.4 GHz to 24 GHz. This result is consistent with the standard theory of compact extragalactic radio sources and suggests that reference frames defined at these higher radio frequencies will be less susceptible to the effects of intrinsic source structure than those defined at lower frequencies.
    Keywords: Astronomy
    Type: International VLBI Service for Geodesy and Astrometry 2004 General Meeting Proceedings; 75-79; NASA/CP-2004-212255
    Format: application/pdf
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  • 4
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    Low Cost, Low Power, Passive Muon Telescope for Interrogating Martian Sub-Surface (2012)
    In:  Other Sources
    Details
    Publication Date: 2019-08-13
    Description: It has been demonstrated on Earth that a low power, passive muon detector can penetrate deep into geological structures up to several kilometers in size providing high density images of their interiors. Muon tomography is an entirely new class of planetary instrumentation that is ideally suited to address key areas in Mars Science, such as: the search for life and habitable environments, the distribution and state of water and ice and the level of geologic activity on Mars today.
    Keywords: Lunar and Planetary Science and Exploration
    Type: Concepts and Approaches for Mars Exploration Workshop; 12 - 14, Jun. 2012; Houston, TX; United States
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  • 5
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    Mission Implementation Constraints on Planetary Muon Radiography (2011)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Cost: Use heritage hardware, especially use a tested landing system to reduce cost (Phoenix or MSL EDL stage). The sky crane technology delivers higher mass to the surface and enables reaching targets at higher elevation, but at a higher mission cost. Rover vs. Stationary Lander: Rover-mounted instrument enables tomography, but the increased weight of the rover reduces the allowable payload weight. Mass is the critical design constraint for an instrument for a planetary mission. Many factors that are minor factors or do not enter into design considerations for terrestrial operation are important for a planetary application. (Landing site, diurnal temperature variation, instrument portability, shock/vibration)
    Keywords: Lunar and Planetary Science and Exploration
    Type: International Workshop on High Energy Geophysics 2011; Oct 27, 2011 - Oct 28, 2011; Tokyo; Japan
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  • 6
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    VLBI and Transients: Very Long Baseline Interferometry and Pulses (2013)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking; Spacecraft Instrumentation and Astrionics
    Type: Interferometric Techniques for Impulsive Signals at Radio/Microwave Frequencies; Apr 22, 2013 - Apr 24, 2013; Columbus, OH; United States
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  • 7
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    Improved Spacecraft Tracking and Navigation Using a Portable Radio Science Receiver (2013)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Portable Radio Science Receiver (PRSR) is a suitcase-sized open-loop digital receiver designed to be small and easy to transport so that it can be deployed quickly and easily anywhere in the world. The PRSR digitizes, downconverts, and filters using custom hardware, firmware, and software. Up to 16 channels can be independently configured and recorded with a total data rate of up to 256 Mbps. The design and implementation of the system's hardware, firmware, and software is described. To minimize costs and time to deployment, our design leveraged elements of the hardware, firmware, and software designs from the existing full-sized operational (non-portable) Radio Science Receivers (RSR) and Wideband VLBI Science Receivers (WVSR), which have successfully supported flagship NASA deep space missions at all Deep Space Network (DSN) sites. We discuss a demonstration of the PRSR using VLBI, with one part per billion angular resolution: 1 nano-radian / 200 ?as synthesized beam. This is the highest resolution astronomical instrument ever operated solely from the Southern Hemisphere. Preliminary results from two sites are presented, including the European Space Agency (ESA) sites at Cebreros, Spain and Malargue, Argentina. Malargue's South American location is of special interest because it greatly improves the geometric coverage for spacecraft navigation in the Southern Hemisphere and will for the first time provide coverage to the 1/4 of the range of declination that has been excluded from reference frame work at Ka-band.
    Keywords: Space Communications, Spacecraft Communications, Command and Tracking
    Type: 2013 IEEE Aerospace Conference; Mar 02, 2013 - Mar 09, 2013; Big Sky, MT; United States
    Format: text
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