Engineering topics
Thurman, S.
Publications and source records attributed to Thurman, S..
Rough lander concept for Mars exploration
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Second generation Mars landed missions
This paper addresses some of the candidate missions being considered for the next generation projects, discusses the new approaches being developed to implement safe and accurate entry, descent and landing to the Martian surface, and describes the rover technology that enables the long distance and duration surface mission.
Navigation and Guidance for the Mars Surveyor 1998 Mission
Mars surveyor 98 is part of NASA's Mar Surveyor Program, a scientifically aggressive but tightly cost-constrained program of robotic Mars exploration, with the goal of sending two spacecraft to Mars every two years form 1997 to 2006.
Navigation and Guidance for the Mars Surveyor 1998 Mission
In December, 1998 and January 1999 NASA will launch two spacecraft to Mars as part of the overall Mars Exploration Program managed at JPL. One is an orbiter that will arrive at Mars in October of 1999 carrying a science payload for remote sensing.
Mars Pathfinder Atmospheric Entry Reconstruction
A reconstruction of the Mars atmosphere profile encountered by the Pathfinder entry vehicle will be presented.
Spacecraft-spacecraft radio-metric tracking: Signal acquisition requirements and application to Mars approach navigation
Doppler and ranging measurements between spacecraft can be obtained only when the ratio of the total received signal power to noise power density (P(sub t)/N(sub 0)) at the receiving spacecraft is sufficiently large that reliable signal detection can be achieved within a reasonable time period. In this article, the requirement on P(sub t)/N(sub 0) for reliable carrier signal detection is calculated as a function of various system parameters, including characteristics of the spacecraft computing hardware and a priori uncertainty in spacecraft-spacecraft relative velocity and acceleration. Also calculated is the P(sub t)/N(sub 0) requirements for reliable detection of a ranging signal, consisting of a carrier with pseudonoise (PN) phase modulation. Once the P(sub t)/N(sub 0) requirement is determined, then for a given set of assumed spacecraft telecommunication characteristics (transmitted signal power, antenna gains, and receiver noise temperatures) it is possible to calculate the maximum range at which a carrier signal or ranging signal may be acquired. For example, if a Mars lander and a spacecraft approaching Mars are each equipped with 1-m-diameter antennas, the transmitted power is 5 W, and the receiver noise temperatures are 350 K, then S-band carrier signal acquisition can be achieved at ranges exceeding 10 million km. An error covariance analysis illustrates the utility of in situ Doppler and ranging measurements for Mars approach navigation. Covariance analysis results indicate that navigation accuracies of a few km can be achieved with either data type. The analysis also illustrates dependency of the achievable accuracy on the approach trajectory velocity.
Doppler Navigation of Interplanetary Spacecraft Using Different Data Processing Modes
This paper presents an investigation of the navigation accuracy that can be achieved with two-way coherent X-band Doppler phase and frequency data; both theoretical and practical aspects of the two Doppler formulations are addressed.
Navigation Demonstration of Precision S/X Ban Ranging with the Ulysses Spacecraft
While Earth orbiting spacecraft navigation has routinely been able to use various sorts of range data at accuracies of 2 meters or better, interplanetary spacecraft navigation using long data arcs has had to artificially deweight range data to 1 kilometer or more, ....
Navigation Demonstrations of Precision Ranging with the Ulysses Spacecraft
This paper describes the incorporation of a simple model of solar plasma-induced variations in ranging data into a procedure for reducing ranging data taken near conjunction with an assumed accuracy near the inherent accuracy of the measurements.
Radio Doppler Navigation of Interplanetary Spacecraft Using Different Data Processing Modes
Doppler shift measurements derived from closed-loop radio tracking of distant spacecraft by ground stations of the Deep Space Network (DSN) are one of the principal means used for interplanetary navigation.