The Lunar Orbiter Laser Altimeter Investigation on the Lunar Reconnaissance Orbiter Mission

The Lunar Orbiter Laser Altimeter (LOLA) is an instrument on the payload of NASA’s Lunar Reconnaissance Orbiter spacecraft (LRO) (Chin et al., in Space Sci. Rev. 129:391–419, 2007). The instrument is designed to measure the shape of the Moon by measuring precisely the range from the spacecraft to the lunar surface, and incorporating precision orbit determination of LRO, referencing surface ranges to the Moon’s center of mass. LOLA has 5 beams and operates at 28 Hz, with a nominal accuracy of 10 cm. Its primary objective is to produce a global geodetic grid for the Moon to which all other observations can be precisely referenced.     

Crater detection via genetic search methods to reduce image features

Recent approaches to crater detection have been inspired by face detection’s use of gray-scale texture features. Using gray-scale texture features for supervised machine learning crater detection algorithms provides better classification of craters in planetary images than previous methods. When using Haar features it is typical to generate thousands of numerical values from each candidate crater image. This magnitude of image features to extract and consider can spell disaster when the application is an entire planetary surface. One solution is to reduce the number of features extracted and considered in order to increase accuracy as well as speed. Feature subset selection provides the operational classifiers with a concise and denoised set of features by reducing irrelevant and redundant features. Feature subset selection is known to be NP-hard. To provide an efficient suboptimal solution, four genetic algorithms are proposed to use greedy selection, weighted random selection, and simulated annealing to distinguish discriminate features from indiscriminate features. Inspired by analysis regarding the relationship between subset size and accuracy, a squeezing algorithm is presented to shrink the genetic algorithm’s chromosome cardinality during the genetic iterations. A significant increase in the classification performance of a Bayesian classifier in crater detection using image texture features is observed.     

Searching for biosignatures using electron paramagnetic resonance (EPR) analysis of manganese oxides

Manganese oxide (Mn oxide) minerals from bacterial sources produce electron paramagnetic resonance (EPR) spectral signatures that are mostly distinct from those of synthetic simulants and abiogenic mineral Mn oxides. Biogenic Mn oxides exhibit only narrow EPR spectral linewidths (～500 G), whereas abiogenic Mn oxides produce spectral linewidths that are 2-6 times broader and range from 1200 to 3000 G. This distinction is consistent with X-ray structural observations that biogenic Mn oxides have abundant layer site vacancies and edge terminations and are mostly of single ionic species [i.e., Mn(IV)], all of which favor narrow EPR linewidths. In contrast, abiogenic Mn oxides have fewer lattice vacancies, larger particle sizes, and mixed ionic species [Mn(III) and Mn(IV)], which lead to the broader linewidths. These properties could be utilized in the search for extraterrestrial physicochemical biosignatures, for example, on Mars missions that include a miniature version of an EPR spectrometer.     

Einstein observations of hot stars

Surveys with instruments on the $\text{Einstein Observatory}$ have shown that essentially all 0 and B main sequence stars are X-ray sources as are many, if not all, 0B supergiants and Wolf-Rayet stars. The X-ray luminosities are sufficient to explain broad lines from the superionization stages seen in the UV spectra of the stars. High energy resolution spectra from the Solid State Spectrometer are shown to place severe constraints on various models for the location of the X-ray sources in the outer atmospheres of the stars. Coronal and embedded shock models for the X-ray emission are discussed and each is found to have some problems in explaining the X-ray emission of 0B stars. X-ray line emission of Si XIII and S XV in ? Ori is discussed and interpreted as arising from magnetically confined loops.     

Columbia and Challenger: organizational failure at NASA

The National Aeronautics and Space Administration (NASA)—as the global leader in all areas of spaceflight and space science—is a unique organization in terms of size, mission, constraints, complexity and motivations. NASA's flagship endeavor—human spaceflight—is extremely risky and one of the most complicated tasks undertaken by man. It is well accepted that the tragic destruction of the Space Shuttle Challenger on 28 January 1986 was the result of organizational failure. The surprising disintegration of the Space Shuttle Columbia in February 2003—nearly 17 years to the day after Challenger—was a shocking reminder of how seemingly innocuous details play important roles in risky systems and organizations. NASA as an organization has changed considerably over the 42 years of its existence. If it is serious about minimizing failure and promoting its mission, perhaps the most intense period of organizational change lies in its immediate future. This paper outlines some of the critical features of NASA's organization and organizational change, namely path dependence and “normalization of deviance”. Subsequently, it reviews the rationale behind calling the Challenger tragedy an organizational failure. Finally, it argues that the recent Columbia accident displays characteristics of organizational failure and proposes recommendations for the future.     

ISU design projects : A new instrument for shaping global space policy?

The author argues that students attending the International Space University (ISU) are becoming a force to be reckoned with in space activities thanks to their enthusiasm, dedication and their Design Projects tackling major technological issues. This article reviews previous projects, before focusing on those of 1993 and 1994, and analyses whether they can be seen as agents for change in space policy making. Key ‘selling points’ are the ‘students’ non-rigid approach to thinking and doing, their refusal to believe in the intractability of any problem and the appeal their novel coalition may have for political leaders.     

DF Vectoring: Application to Stationary Synchronous Satellites

Several methods of using an earth-based radio reference signal to determine the three-axis attitude of a synchronous satellite, and two types of spacecraft electronic systems (amplitude measurement and phase measurement), which obtain attitude and pointing information from the radio reference signal for orientating the spacecraft and for directing large-aperture antennas aboard the spacecraft are described. The earth-based radio reference signal also enables the electronic systems to determine angles to other ground stations with respect to fixed (reference) stations on the earth. These attitude- and angle-determining techniques are applicable to communications satellites, navigational satellites, and intersatellite data relay systems.     

Survey of mission evolution and flexibility in the Space Shuttle program

Given the diversity of missions it has accomplished and the myriad of adaptations it has undergone, the US Space Shuttle is widely regarded as a highly flexible space vehicle. With the Shuttle’s upcoming 2011 retirement, it is instructive to survey the history of this vehicle’s flexibility for the insights it can provide to the design and characterization of flexibility in future space systems. Data are presented on the evolution of mission requirements over time for 120 missions performed by the Space Shuttle over a period of some 27 years. Distinct trends in the time domain – as well as their causes – are identified and discussed, and early manifest plans from 1982 serve as a confirmation that these trends were not originally anticipated. Eight examples are then presented of engineering modifications that allowed the Shuttle to adapt and accommodate these requirement changes. Several additional instances of Shuttle flexibility are explored, such as post-Columbia disaster modification, upgrade programs and derived vehicles, and one case in which flexibility was inhibited by an early design decision.     

A Stepping Motor Drive Circuit Using Magnetic Core Logic

A new magnetic core circuit that is used to supply power in the proper phase and time sequence to a bidirectional stepping motor is described. This circuit will power a standard voltage stepping motor from a nonstandard voltage power supply and includes a means for maintaining a constant energy pulse excitation over a wide range of dc power supply input voltage, a means for supplying power to the winding of the motor on pairs of isolated conductors, and a means for conductively isolating the low-level logic circuits from the high-level power circuits.     

The management of the geostationary environment

The population in the geostationary orbit is increasing at the rate of about 25 spacecraft a year and operating lifetimes are increasing. The size of the spacecraft is increasing, as is the power level. The only way to protect the operational arc is to reboost spacecraft at end of life to a burial orbit. While most operators do some reboost maneuver at end of mission there has been no agreed upon criterion for the maneuver. The ITU-R S. 1003¹ recommends reboost of not less than 300 km with the apogee as high as possible. The Interagency Debris Coordination Working Group (IADC) has recently achieved a consensus on a recommendation that the minimum maneuver be 235 km + Cr 1000 A/M. The concept is that this accommodates the ± 3 7.5 km variance in normal radial positioning and a 167.5 km corridor above the arc for repositioning or supersynchronous delivery and establishes a criterion by which the dispositioned spacecraft will never enter that zone after its completion of the maneuver. It also deals with the fact the area mass ratio of spacecraft has been evolving to higher values. Earlier spacecraft had characteristic values of 0.03 but the average now is closer to 0.05 and there are some as great as 0.10.

Disposition of the upper stage should be the same as the spacecraft if it is delivered to GSO. It is preferable to have the stage deliver the spacecraft supersynchronous and then have the spacecraft maneuver down to the GSO.