Engineering topics
Publications and source records attributed to Romans, L..
The two GRACE (Gravity Recovery and Climate Experiment) spacecraft were launched into a near polar circular orbit around the earth in March of 2002. The two spacecraft serve as test masses to measure the Earth's gravitational field.
In this paper, we describe the mission design for TPF assuming a distributed spacecraft concept using formation flight around both a halo orbit around L2 as well as a heliocentric orbit. Although the mission architecture is still under study, the next two years will include study of four design cncepts and a downselect to two concepts around 2005.
The Gravity Recovery and Climate Experiment launched March 17, 2002. The GPS data for this experiment are processed to contribute to the recover long wavelength gravity field; remove errors due to long term on-board oscillator drift; and align K/Ka-band measurments between the two spacecraft to 0.1 ns. This paper will concentrate on the use of GPS for these timing and calibration functions and will not address the recovery of the gravity field.
In this paper, we will describe some of the underlying principles of QGC, discuss its potential capability, and report on the progress of our hardware development to date.
We present the first spaceborne observation of a Global Positioning System (GPS) signal reflected from the Earth's surface, specifically from the Pacific Ocean.
In this paper we present results for CHAMP POD using the precise GPS measurements collected by the BlackJack receiver through the up-looking antenna. We will describe the quality of the tracking data, the tuning of the reduced-dynamic model for the 400-km orbit, and the various methods of evaluating the orbit accuracy.
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The BlackJack family of GPS receivers has been developed at JPL to satisfy NASA's requirements for high-accuracy, dual-frequency, Y-codeless GPS receivers for NASA's Earth science missions. In this paper we will present the challenges that were overcome to meet this accuracy requirement. We will discuss the various reduced dynamic strategies, Space Shuttle dynamic models, and our tests for accuracy that included a military Y-code dual-frequency receiver (MAGR).
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As our civilization becomes more dependent on space based technologies, we become more vulnerable to conditions in space weather. Accurate space weather specification and forecasting require proper modeling which account for the coupling between the sun, the magnetosphere, the thermosphere, the ionosphere and the mesosphere.
We present results of combining occultation refractivity profiles from GPS/MET with ECMWF global analyses in a 1DVar framework in order to separate the wet and dry contributions to refractivity and assess their impact on the analyzed temperature, surface pressure and specific humidity fields.
In recent years, the Global Positioning System (GPS) has been exploited via radio occultation techniques to obtain profiles of refractivity, temperature, pressure and water vapor in the neutral atmosphere and electron density in the ionosphere.
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Mars has become the focus of an unprecedented series of missions spanning many years, involving numerous nations and evolving from robotics to humans.
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