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You, Tung-Han

Publications and source records attributed to You, Tung-Han.

25 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Atmosphere variability at Mars Reconnaissance Orbiter science orbit altitudes based on Mars Express Reconstructions

This paper describes the orbit reconstruction of Mars Express (MEX) with the specific goal of estimating the atmospheric density near periapsis and evaluating its variability and predictability. The desired outcome is to validate the covariance analysis assumption of atmospheric variability for the 2005 NASA Mars Reconnaissance Orbiter (MRO), as well as evaluate the accuracy of the density estimates output from the atmosphere model used by MRO. Topics covered include the MRO atmosphere model, MEX orbit determination and post-fit Doppler residuals, and atmosphere trending statistics gleaned from the orbit reconstructions.

Higas, Earl↗
NASA NTRS2004

Mars Reconnaissance Orbiter Navigation

Mars Reconnaissance Orbiter will launch in August 2005 at Cape Canaveral Air Force Station. The heavyweight spacecraft will use a Lockheed-Martin Atlas V-401 launch vehicle. It will be the first mission in a low Mars Orbit to characterize the surface, subsurface, and atmospheric properties. The intensive science operation imposes a great challenge for Navigation to satisfy the stringent requirements. This paper describes navigation key requirements, major challenges, and the sophisticated dynamic modeling. It also details navigation strategy and processes for various mission phases. Mars Reconnaissance Orbiter will return significant amount of scientific data in support of the objectives set by the Mars Exploration Program. A robust and precise navigation is the key to the success of this mission.

navigation↗
NASA NTRS2004

The Mars Reconnaissance Orbiter mission plan

This paper describes the Mars Reconnaissance Orbiter Mission Plan with emphasis on major mission activities and key challenges in mission design, spacecraft design, and science data acquisition.

Jah, Moriba↗
NASA NTRS1995

Magellan aerobrake navigation

The Magellan spacecraft has been aerobraked into a 197 x 541 km near-circular orbit around Venus from which it is conducting a high-resolution gravity mapping mission. This was the first interplanetary aerobrake maneuver and involved flying the spacecraft through the upper reaches of the Venusian atmosphere 730 times over a 70 day period. Round-trip light-time varied from 9.57 to 18.83 minutes during this period. Navigation for this dynamic phase of the Magellan mission was planned and executed in the face of budget-driven down-sizing with all spacecraft safe modes disabled and a flight-team one-third the size of comparable interplanetary missions. Successful execution of this manuever using spacecraft hardware not designed to operate in a planetary atmosphere, demonstrated a practical cost-saving technique for both large and small future interplanetary missions.

Giorgini, Jon↗
NASA NTRS1994

(abstract) Navigating through the Venus Atmosphere

This paper presents the problems and challenges of the Magellan Navigation Team. The challenges are: 1) to predict the periapsis time to an accuracy of less than 100 seconds, 2) to accurately predict the dynamic pressure incurred by the spacecraft, 3) to model and to generate this prediction in a timely manner, 4) to provide navigation support 7 days per week for 70 days with 3 navigators and one graphic specialist to generate a daily package for presentation and display. The problems encountered by the Navigation Team in order to meet the above challenges are: 1) the uncertainty in the Venus atmosphere model, 2) the uncertainty in the Venus gravity model, 3) the uncertainty in predicting the attitude control thruster firing, 4) the sparse amount of radiometric tracking data, 5) the radiometric data editing is complicated by the effects of the Venus atmosphere fluctuations.

Venus↗
NASA NTRS1992

Magellan navigation using X-band differenced Doppler during Venus mapping phase

This paper describes Magellan navigation procedures and performance during the first 1.5 years of mapping. It presents the results of studies comparing several orbit determination methods performed with and without X-band (8.4 GHz) differenced Doppler tracking data. X-band differenced Doppler has been used as a primary navigation data-type for the first time. It has been found to be a significant aid in efficiently meeting orbiter navigation requirements during the Magellan spacecraft's Venus radar-mapping phase.

Giorgini, Jon D.↗