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Preliminary Design of the Guidance, Navigation, and Control System of the Altair Lunar LanderGuidance, Navigation, and Control (GN&C) is the measurement and control of spacecraft position, velocity, and attitude in support of mission objectives. This paper provides an overview of a preliminary design of the GN&C system of the Lunar Lander Altair. Key functions performed by the GN&C system in various mission phases will first be described. A set of placeholder GN&C sensors that is needed to support these functions is next described. To meet Crew safety requirements, there must be high degrees of redundancy in the selected sensor configuration. Two sets of thrusters, one on the Ascent Module (AM) and the other on the Descent Module (DM), will be used by the GN&C system. The DM thrusters will be used, among other purposes, to perform course correction burns during the Trans-lunar Coast. The AM thrusters will be used, among other purposes, to perform precise angular and translational controls of the ascent module in order to dock the ascent module with Orion. Navigation is the process of measurement and control of the spacecraft's "state" (both the position and velocity vectors of the spacecraft). Tracking data from the Earth-Based Ground System (tracking antennas) as well as data from onboard optical sensors will be used to estimate the vehicle state. A driving navigation requirement is to land Altair on the Moon with a landing accuracy that is better than 1 km (radial 95%). Preliminary performance of the Altair GN&C design, relative to this and other navigation requirements, will be given. Guidance is the onboard process that uses the estimated state vector, crew inputs, and pre-computed reference trajectories to guide both the rotational and the translational motions of the spacecraft during powered flight phases. Design objectives of reference trajectories for various mission phases vary. For example, the reference trajectory for the descent "approach" phase (the last 3-4 minutes before touchdown) will sacrifice fuel utilization efficiency in order to provide landing site visibility for both the crew and the terrain hazard detection sensor system. One output of Guidance is the steering angle commands sent to the 2 degree-of-freedom (dof) gimbal actuation system of the descent engine. The engine gimbal actuation system is controlled by a Thrust Vector Control algorithm that is designed taking into account the large quantities of sloshing liquids in tanks mounted on Altair. In this early design phase of Altair, the GN&C system is described only briefly in this paper and the emphasis is on the GN&C architecture (that is still evolving). Multiple companion papers will provide details that are related to navigation, optical navigation, guidance, fuel sloshing, rendezvous and docking, machine-pilot interactions, and others. The similarities and differences of GN&C designs for Lunar and Mars landers are briefly compared.
Document ID
20150008922
Acquisition Source
Jet Propulsion Laboratory
Document Type
Conference Paper
External Source(s)
Authors
Lee, Allan Y.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Ely, Todd
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Sostaric, Ronald
(NASA Johnson Space Center Houston, TX, United States)
Strahan, Alan
(NASA Johnson Space Center Houston, TX, United States)
Riedel, Joseph E.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Ingham, Mitch
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Wincentsen, James
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Sarani, Siamak
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
May 26, 2015
Publication Date
August 2, 2010
Subject Category
Space Communications, Spacecraft Communications, Command And Tracking
Astrodynamics
Spacecraft Design, Testing And Performance
Lunar And Planetary Science And Exploration
Meeting Information
Meeting: AIAA Guidance, Navigation, and Control Conference
Location: Toronto, ON
Country: Canada
Start Date: August 2, 2010
End Date: August 5, 2010
Sponsors: American Inst. of Aeronautics and Astronautics
Distribution Limits
Public
Copyright
Other

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