Lunar Orbiter Mission Research Articles

Reduction of Lunar Landing Fuel Requirements by Utilizing Lunar Ballistic Capture

Ballistic lunar capture trajectories have been successfully utilized for lunar orbital missions since 1991. Recent interest in lunar landing trajectories has occurred due to a directive from President Bush to return humans to the Moon by 2015. NASA requirements for humans to return to the lunar surface include separation of crew and cargo missions, all lunar surface access, and anytime-abort to return to Earth. Such requirements are very demanding from a propellant standpoint. The subject of this paper is the application of lunar ballistic capture for the reduction of lunar landing propellant requirements. Preliminary studies of the application of weak stability boundary (WSB) trajectories and ballistic capture have shown that considerable savings in low Earth orbit (LEO) mission mass may be realized, on the order of 36% less than conventional Hohmann transfer orbit missions. Other advantages, such as reduction in launch window constraints and reduction of lunar orbit maintenance propellant requirements, have also surfaced from this study.

India, China Vie for Best Look at the Moon

UDAIPUR, INDIA —The new kids on the space block are having their own race to the moon. Last week, at an international meeting here[*][1] on lunar exploration, Chinese scientists presented details of the country's planned lunar orbiter mission, named Chang'e, to be launched sometime in 2007. Not to

Possibilities of lunar polar orbiter

It appears very likely that early next century a lunar base and a manned outpost on Mars will be established through international collaboration to explore and utilize the Moon and Mars. In order to contribute to these projects, National Space Development Agency of Japan (NASDA) has conducted the preliminary studies. As for the lunar projects, possibilities of a lunar polar orbiter (LPO), robotic rover, and sample return mission have been investigated. This paper describes the concept of the LPO based on the H-II rocket and earth observation technology of Japan. The LPO will map the global surface, especially the polar region and the farside of the Moon from 100 km lunar polar orbit and send the precise images of various wave length, acquired by onboard sensors to the Earth. The primary purpose of the LPO is to identify global and local structures of lunar resources and topography and to search for a suitable site for the lunar base.

Application of MPD thruster systems to interplanetary missions

Studies of space tests and applications of MPD thruster systems in the 1990s are described. They include the Advanced Space Experiment onboard the Space Flyer Unit (SFU) in low Earth orbit (LEO), the lunar polar orbiter mission in the early 1990s, and the asteroid rendezvous mission in the late 1990s. The SFU uses a 5 kw MPD thruster system (4 x 1.25 kW system) to assess the on-orbit performance and the potential impact on the LEO environment by thruster plasma injection. During the lunar mission, a 1.25 kW MPD thruster system lowers the orbiter from a high lunar polar orbit into a low orbit less than 100 kW in altitude. These early applications can be followed by an interplanetary asteroid rendezvous mission. Envisioning these missions, the MPD thruster system is required to have 10 X10 pulse lifetime and to generate 40 mN/kW at a specific impulse of 2000 s.

Measuring planetary neutron albedo fluxes by remote gamma-ray sensing

A remote-sensing γ-ray spectrometer (GRS) is capable of measuring planetary surface composition through the detection of characteristic gamma rays. In addition, the planetary neutron leakage flux may be detected by means of a thin neutron absorber surrounding the γ-ray detector which converts the neutron flux into a γ-ray flux having a unique energy signature. The γ rays representing the neutron flux are observed against interference consisting of cosmic γ rays, planetary continuum and line emission, and a variety of gamma rays arising from cosmic-ray particle interactions with the γ-ray spectrometer and spacecraft (SC). In this paper the amplitudes of planetary and non-planetary neutron fluxes are assessed and their impact on the sensitivity of measurement is calculated for a lunar orbiter mission and a comet nucleus rendezvous mission. For a 100 h observation period from an altitude of 100 km, a GRS on a lunar orbiter can detect a thermal neutron albedo flux as low as 0.002 cm −2 s −1 and measure the expected flux of ∼ 0.6 cm −2 s −1 with an uncertainty of 0.001 cm −2 s −1. A GRS rendezvousing with a comet at a distance equal to the radius of the comet's nucleus, again for a 100 h observation time, should detect a thermal neutron albedo flux at a level of 0.006 cm −2 s −1 and measure the expected flux of ∼ 0.4 cm −2 s −1 with an uncertainty of 0.004 cm −2 s −1. Mapping the planetary neutron flux jointly with the direct detection of H will not only provide a more accurate model for translating observed γ-ray fluxes into concentrations but will also extend the effective sampling depth and should provide a capability for simple stratigraphic modeling of hydrogen.

An improved lunar moment of inertia determination: a proposed strategy

The current error of 0.0025 on the lunar homogeneity parameterI/MR 2 is dominated by the uncertainties in theC 20 andC 22 gravity harmonics. This error level is equivalent to a 4.20 gm cm−3 density uncertainty for a lunar interior model having a core 300 km in radius. Covariance analyses are performed using Doppler data from the relay satellite of the proposed Lunar Polar Orbiter mission to determine an optimum reduction strategy which obtains an order of magnitude improvement in the gravity estimates. Error studies show the long-arc reduction method obtains results which are an order of magnitude more accurate than the short-arc technique. The nominal 4000 km circular orbit of the relay satellite is very sensitive to the unmodeled effects of gravity harmonics of degree 5 through 9. Results from this orbital geometry indicate that it may not be possible to achieve the desired order of magnitude accuracy improvement. A modified orbit having the identical orbital conditions as the nominal one, but with a larger semi-major axis of 7000 km is studied. Results show the desired order of magnitude improvement can be achieved when a complete fourth degree and order model and some fifth and sixth degree terms are estimated while considering the unmodeled effects of the remaining harmonics through degree and order eight. Studies also show a 50% additional improvement inC 22 can be achieved if differential differenced Doppler is also processed with the direct Doppler. The improved uncertainty inI/MR 2 reduces the core density error from 4.20 gm cm−3 to 0.1 gm cm−3 for the case of a lunar density model having a 300 km core radius.

Lateral displacement pattern in the Humorum region

Medium- to high-resolution photographs taken by the Lunar Orbiter missions of the Humorum region show a definite pattern of lateral displacements of topographic elements and en echelon arrangement of crenulations upon mare ridges. The southern wall of Gassendi crater has been dextrally offset for distances up to 6 km along east-southeast faults. Towards the west the strike-slip faults continue into highland material as bands up to 10 km wide of sinistral en echelon fractures, while towards the east the same faults transform into mare ridges with sinistral en echelon crestal crenulations. It is, therefore, very probable that the en echelon crenulations represent igneous rock intruded into or extruded through tension gashes which developed in lava that overlie strike-slip faults and through movement along these faults. The pattern of commonly recurring lineament strikes and sense of wrench faulting corresponds to a generating stress system in which the regional maximum compression acted between 10 and 20° and the intermediate compression was directed vertically. Lineaments that strike northeast and those trending within the northwest quadrant show indications of slip in left-lateral and right-lateral sense, respectively.

Opportunity to participate in NASA LPO mission

The National Aeronautics and Space Administration (NASA) has issued an Announcement of Opportunity (AO) providing information and guidelines for prospective investigators who are interested in participating in the Lunar Polar Orbiter (LPO) mission, tentatively planned for a June 1980 launch.The LPO will be a cost‐limited geochemical, geophysical, and geological mission capable of extending to the entire moon the orbital and surface science results obtained from previous lunar missions, expecially Apollo. Because of the applicability of LPO objectives and concepts to the exploration of planetary bodies with limited atmospheres, this mission may serve as a scientific prototype for similar missions to Mars and to Mercury.

An empirically derived lunar gravity field

A new method has been devised to determine spherical harmonic coefficients of the lunar gravity field. This method uses a two-step data reduction and estimation process. The first step applies a weighted least-squares empirical orbit determination process to Doppler tracking data to estimate long-period Kepler elements and rates. In the second step, lunar gravity coefficients are determined using another weighted least-squares processor which fits the long-period Lagrange perturbation equations to the estimated Keplerian rates. This method has been applied to tracking data from the Lunar Orbiter missions. A gravity potential of degree and order four is presented and error sources discussed. Plots of lunar equipotential surfaces are shown. Gravity field results are applied to various physical properties of the Moon such as moments and products of inertia. This gravity field has been investigated using data from several Apollo missions. Solutions from these data, in all cases except that of Apollo 15, result in improved orbit predictions as compared to those using other fields. All solutions indicate that the field models are still imcomplete.

Lunar Orbiter mission design.

The primary objectives of the Lunar Orbiter Program were to obtain photographic coverage of potential Apollo and Surveyor landing sites on the moon and to contribute to the scientific knowledge of the moon. An additional objective was to obtain information on the gravitational field of the moon. The landing site search at 1-m resolution was essentially completed by the end of the third flight; remaining flights provided a 100-m resolution map of the lunar front side and closeup views of scientifically interesting sites. The lunar back side was covered at about 1 km resolution. In this paper the lunar orbit design is developed in terms of mission requirements and predicted effects due to Earth and lunar gravitational fields. Errors experienced in predicting the spacecraft trajectory during the flight are indicated to be due to large irregularities in the lunar gravitational field.

Synopsis: Horizons in Guidance Computer Component Technology

An extensive survey of semiconductor and memory component manufacturers conducted by the Electronics Research Center of NASA and industry has resulted in estimates of the state of the art of components available to designers of on-board guidance and control computers for long-term, deep-space missions for the 1970-1972 period. The vehicle for the survey was the mission requirements for the synchronous satellite, lunar orbiter, Mars orbiter, and Jupiter fly-by solar probe missions.

Horizons in Guidance Computer Component Technology

Abstract—An extensive survey of logic and memory component manufacturers conducted by the NASA Electronic Research Center and the industry has resulted in estimates of the state-of-the-art of components available to designers of on-board guidance and control computers for long-term deep-space missions for the 1970-72 period. The vehicle for the survey were the mission requirements for the synchronous satellite, lunar orbiter, Mars orbiter, and Jupiter fly-by solar probe missions.

The Lunar Orbiter Photographic System

The photographic system which produced the photographs of the lunar surface is a complex one. Inherent in its design is provision for dual lens photography, film processing, conversion of the film images into video signals for relay through the spacecraft transmitter and reconstitution of the photographic image on earth after receipt of signals by the orbital tracking stations. The prime objective of the Lunar Orbiter Mission is to secure topographic data of the lunar surface to enable selection and confirmation of suitable Apollo landing sites. In addition to the stringent performance objectives, the equipment design was strongly influenced by a number of constraints: e.g., size, weight, power consumption, pressure environment, the ambient thermal environment and the limitation on system control and instrumentation. Fundamental to the photographic system design was the selection of a suitable film processing chemistry and lenses. These are all reviewed in detail. The performance photographic requirements for the ground equipment are also briefly discussed.

Lunar orbiter command and telemetry data handling system (CTDH) at deep space stations

The Lunar Orbiter will provide extensive photographic exploration of the lunar surface to aid in the selection of possible landing areas for Project Apollo manned landing mission. The Lunar Orbiter project* is one of the lunar and planetary programs directed by the NASA Langley Research Center. The Boeing Company is the prime spacecraft contractor. There will be five flight spacecraft and three ground test spacecraft. The first flight is scheduled in the middle of 1966. The Lunar Orbiter mission is supported by the Deep Space Network (DSN). The DSN consists of the Space Flight Operations Facility (SFOF), the Deep Space Instrumentation Facility (DSIF) and intersite communication links. The Jet Propulsion Laboratory operates the DSN and provides mission support for the Lunar Orbiter project.