ALBERT

Description: We present Monte Carlo analysis and experimental data from a novel lithium-drifted silicon detector stack for gamma ray spectroscopy instrumentation in future Mars surface landers and other planetary missions. The Monte Carlo analysis shows full energy photopeaks even in the range of about 100 keV to 2 MeV where, in Si, Compton scattering dominates the absorption processes. Laboratory data is shown for an experimental detector stack of four planar Si(Li) devices, each 5 mm thick with an active area 2 cm in diameter. All the experimental data were collected with maximum temperature of the stack at 175 K. Background reduction is achieved by using the detector of the stack closest to the source in anticoincidence. We present a comparison of experimental data from the stack with the Monte Carlo model for Cs-137 (662 keV). Agreement is shown to be good, with a full energy photopeak clearly seen (FWHM about 10 keV). Experimental stack data is also shown for multiple peaks at 511 keV (Na-22) and 662 keV (Cs-137). The peaks are clearly resolved (FWHM 10 keV), and are compared with the results obtained using a 8 percent resolution, 3 in. x 3 in. NaI(TI) device (FWHM about 50 keV).

Description: Three small inexpensive mission concepts for Mars landing and exploration are described emphasizing expected scientific returns that can lead to human exploration. The Mars Explorer mission prepares for human missions by means of landing-site reconnaissance and characterization, while the Surface Lander Investigation of Mars mission uses a single probe and robotics to image the surface and analyze samples. The Mars Environmental Survey experiment is reported in which robotics are employed to study the soil, atmosphere, weather and seismic activity on the red planet.

Description: In-situ observations and measurements of Mars are objectives of a feasibility study beginning at the Ames Research Center for a mission called the Mars Environmental SURvey (MESUR). The purpose of the MESUR mission is to emplace a pole-to-pole global distribution of landers on the Martian surface to make both short- and long-term observations of the atmosphere and surface. The basic concept is to deploy probes which would directly enter the Mars atmosphere, provide measurements of the upper atmospheric structure, image the local terrain before landing, and survive landing to perform meteorology, seismology, surface imaging, and soil chemistry measurements. MESUR is intended to be a relatively low-cost mission to advance both Mars science and human presence objectives. Mission philosophy is to: (1) 'grow' a network over a period of years using a series of launch opportunities, thereby minimizing the peak annual costs; (2) develop a level-of-effort which is flexible and responsive to a broad set of objectives; (3) focus on science while providing a solid basis for human exploration; and (4) minimize project cost and complexity wherever possible. In order to meet the diverse scientific objectives, each MESUR lander will carry the following strawman instrument payload consisting of: (1) Atmospheric structure experiment, (2) Descent and surface imagers, (3) Meteorology package, (4) Elemental composition instrument, (5) 3-axis seismometer, and (6) Thermal analyzer/evolved gas analyzer. The feasibility study is primarily to show a practical way to design an early capability for characterizing Mars' surface and atmospheric environment on a global scale. The goals are to answer some of the most urgent questions to advance significantly our scientific knowledge about Mars, and for planning eventual exploration of the planet by robots and humans.

Description: An important element of the Space Shuttle Orbiter safety improvement plan is the improved understanding of its aerodynamic performance so as to minimize the "black zones" in the contingency abort trajectories [1]. These zones are regions in the launch trajectory where it is predicted that, due to vehicle limitations, the Orbiter will be unable to return to the launch site in a two or three engine-out scenario. Reduction of these zones requires accurate knowledge of the aerodynamic forces and moments to better assess the structural capability of the vehicle. An interesting aspect of the contingency abort trajectories is that the Orbiter would need to achieve angles of attack as high as 60deg. Such steep attitudes are much higher than those for a nominal flight trajectory. The Orbiter is currently flight certified only up to an angle of attack of 44deg at high Mach numbers and has never flown at angles of attack larger than this limit. Contingency abort trajectories are generated using the data in the Space Shuttle Operational Aerodynamic Data Book (OADB) [2]. The OADB, a detailed document of the aerodynamic environment of the current Orbiter, is primarily based on wind-tunnel measurements (over a wide Mach number and angle-of-attack range) extrapolated to flight conditions using available theories and correlations, and updated with flight data where available. For nominal flight conditions, i.e., angles of attack of less than 45deg, the fidelity of the OADB is excellent due to the availability of flight data. However, at the off-nominal conditions, such as would be encountered on contingency abort trajectories, the fidelity of the OADB is less certain. The primary aims of a recent collaborative effort (completed in the year 2001) between NASA and Boeing were to determine: 1) accurate distributions of pressure and shear loads on the Orbiter at select points in the contingency abort trajectory space; and 2) integrated aerodynamic forces and moments for the entire vehicle and the control surfaces (body flap, speed brake, and elevons). The latter served the useful purpose of verification of the aerodynamic characteristics that went into the generation of the abort trajectories.

Description: In situ measurements of Mars' surface and atmosphere are the objectives of a novel network mission concept called the Mars Environmental SURvey (MESUR). As envisioned, the MESUR mission will emplace a pole-to-pole global distribution of 16 landers on the Martian surface over three launch opportunites using medium-lift (Delta-class) launch vehicles. The basic concept is to deploy small free-flying probes which would directly enter the Martian atmosphere, measure the upper atmospheric structure, image the local terrain before landing, and survive landing to perform meteorology, seismology, surface imaging, and soil chemistry measurements. Data will be returned via dedicated relay orbiter or direct-to-earth transmission. The mission philosophy is to: (1) 'grow' a network over a period of years using a series of launch opportunities; (2) develop a level-of-effort which is flexible and responsive to a broad set of objectives; (3) focus on Mars science while providing a solid basis for future human presence; and (4) minimize overall project cost and complexity wherever possible.

Description: This paper outlines the key parameters of the manned mission to Mars and presents some top-level requirements, issues, and constraints associated with a manned Mars mission that impact the life support system (LSS). Results are presented of a preliminary analysis for advanced LSSs based on physical/chemical reclamation processes, using as a baseline for the analysis the mission profile of a Split-Sprint class mission for an arrival date at Mars in the year 2009. Special attention is given to the potential cost savings as measured by reducing Mars spacecraft mass in LEO.

Description: A viewgraph describing technologies for entry probes is presented. The topics include: 1) Entry Phase; 2) Descent Phase; 3) Long duration atmospheric observations; 4) Survivability at high temperatures; and 5) Summary.