Engineering topics

Hills, H. Kent

Publications and source records attributed to Hills, H. Kent.

15 records

NASA NTRS2018

History and Status of ALSEP and the Apollo Lunar Data Project

A suite of automated scientific instruments (the Apollo Lunar Surface Experiment Package, or ALSEP) was installed at each of the landing sites of Apollo 12, 14, 15, 16, and 17 from 1969 to 1972. They operated from deployment until decommissioning on 30 September 1977. These data were continuously transmitted to Earth and saved on the Range Tapes, which were recorded at the Manned Space Flight Network stations. These data were also broken out by experiment and sent to the experiment Principal Investigators on what were called the P.I. Tapes. Starting in April 1973 the Range Tape data were stored in digital format on 7-track magnetic tapes, the ARCSAV Tapes. In February 1976, the handling of the Range Tapes was transferred to UT Galveston. They produced 9-track tapes referred to as the Work Tapes. Following the Apollo program the Range and ARCSAV tapes, which were never archived, were lost. The Work Tapes were archived at the National Space Science Data Center (NSSDC). Some investigators archived their individual experiment data with NSSDC as well, but much of the data had minimal documentation, were not in digital form, or were stored in difficult to translate formats. Data from many experiments were never delivered to the NSSDC. The Lunar Data Project was started to address the problem of both missing and not readily usable data. Our effort has resulted in recovery of some of the ARCSAV tapes, recovery and digitization of a large volume of Apollo scientific and technical documentation, and restoration of many ALSEP and other Apollo data collections. Restoration involves deciphering formats, assembling necessary ancillary data (metadata), and packaging data in digital format to be archived with the Planetary Data System (PDS). Recovery of the data from the ARCSAV tapes involved having the tapes read on special equipment and extracting the individual experiment data out of the integrated data stream. We will report on the history and status of the various recovery efforts.

Work Tapes↗

NASA NTRS2016

Stair-Step Particle Flux Spectra on the Lunar Surface: Evidence for Nonmonotonic Potentials?

We present examples of unusual "stair‐step" differential flux spectra observed by the Apollo 14 Suprathermal Ion Detector Experiment on the lunar dayside surface in Earth's magnetotail. These spectra exhibit a relatively constant differential flux below some cutoff energy and then drop off precipitously, by about an order of magnitude or more, at higher energies. We propose that these spectra result from photoions accelerated on the lunar dayside by nonmonotonic potentials (i.e.,potentials that do not decay to zero monotonically) and present a model for the expected differential flux. The energy of the cutoff and the magnitude of the differential flux are related to the properties of the local space environment and are consistent with the observed flux spectra. If this interpretation is correct, these surface‐based ion observations provide a unique perspective that both complements and enhances the conclusions obtained by remote‐sensing orbiter observations on the Moon's exospheric and electrostatic properties.

Stair-step↗

NASA NTRS2016

Restoration of Apollo Data by the Lunar Data Project/PDS Lunar Data Node: An Update

The Apollo 11, 12, and 14 through 17 missions orbited and landed on the Moon, carrying scientific instruments that returned data from all phases of the missions, included long-lived Apollo Lunar Surface Experiments Packages (ALSEPs) deployed by the astronauts on the lunar surface. Much of these data were never archived, and some of the archived data were on media and in formats that are outmoded, or were deposited with little or no useful documentation to aid outside users. This is particularly true of the ALSEP data returned autonomously for many years after the Apollo missions ended. The purpose of the Lunar Data Project and the Planetary Data System (PDS) Lunar Data Node is to take data collections already archived at the NASA Space Science Data Coordinated Archive (NSSDCA) and prepare them for archiving through PDS, and to locate lunar data that were never archived, bring them into NSSDCA, and then archive them through PDS. Preparing these data for archiving involves reading the data from the original media, be it magnetic tape, microfilm, microfiche, or hard-copy document, converting the outmoded, often binary, formats when necessary, putting them into a standard digital form accepted by PDS, collecting the necessary ancillary data and documentation (metadata) to ensure that the data are usable and well-described, summarizing the metadata in documentation to be included in the data set, adding other information such as references, mission and instrument descriptions, contact information, and related documentation, and packaging the results in a PDS-compliant data set. The data set is then validated and reviewed by a group of external scientists as part of the PDS final archive process. We present a status report on some of the data sets that we are processing.

Lunar↗

NASA NTRS2014

On Lunar Exospheric Column Densities and Solar Wind Access Beyond the Terminator from ROSAT Soft X-Ray Observations of Solar Wind Charge Exchange

We analyze the Rontgen satellite (ROSAT) position sensitive proportional counter soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the surface brightness in three wedges: two 19 deg wedges (one north and one south) 13-32 deg off the terminator toward the dark side and one wedge 38 deg wide centered on the antisolar direction. The radial profiles of both the north and the south wedges show significant limb brightening that is absent in the 38 deg wide antisolar wedge. An analysis of the soft X-ray intensity increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere based on lunar exospheric models and hybrid simulation results of solar wind access beyond the terminator. Soft X-ray imaging thus can independently infer the total lunar limb column density including all species, a property that before now has not been measured, and provide a large-scale picture of the solar wind-lunar interaction. Because the SWCX signal appears to be dominated by exospheric species arising from solar wind implantation, this technique can also determine how the exosphere varies with solar wind conditions. Now, along with Mars, Venus, and Earth, the Moon represents another solar system body at which SWCX has been observed.

Exospheric↗

NASA NTRS2013

First-Time Analysis of Completely Restored DTREM Instrument Data from Apollo 14 and 15

The Dust, Thermal and Radiation Engineering Measurement (DTREM) packages (figure 1) mounted on the central stations of the Apollo 11, 12, 14, and 15 ALSEPs (Apollo Lunar Surface Experiments Packages) measured the outputs of exposed solar cells and thermistors over time. The goal of the experiment, also commonly known as the dust detector, was to study the long-term effects of dust, radiation, and temperature at the lunar surface on solar cells. The monitors returned data for up to almost 8 years from the lunar surface.

McBride, Marie J.↗

NASA NTRS2012

ROSAT Observations of Solar Wind Charge Exchange with the Lunar Exosphere

We analyze the ROSAT PSPC soft X-ray image of the Moon taken on 29 June 1990 by examining the radial profile of the count rate in three wedges, two wedges (one north and one south) 13-32 degrees off (19 degrees wide) the terminator towards the dark side and one wedge 38 degrees wide centered on the anti-solar direction. The radial profiles of both the north and the south wedges show substantial limb brightening that is absent in the 38 degree wide antisolar wedge. An analysis of the count rate increase associated with the limb brightening shows that its magnitude is consistent with that expected due to solar wind charge exchange (SWCX) with the tenuous lunar atmosphere. Along with Mars, Venus, and Earth, the Moon represents another solar system body at which solar wind charge exchange has been observed. This technique can be used to explore the solar wind-lunar interaction.

Collier, Michael R.↗

NASA NTRS2012

Restoration and Reexamination of Apollo Lunar Dust Detector Data from Original Telemetry Files

We are recovering the original telemetry (Figure I) from the Apollo Dust, Thermal, Radiation Environment Monitor (DTREM) experiment, more commonly known as the Dust Detector, and producing full time resolution (54 second) data sets for release through the Planetary Data System (PDS). The primary objective of the experiment was to evaluate the effect of dust deposition, temperature, and radiation damage on solar cells on the lunar surface. The monitor was a small box consisting of three solar cells and thermistors mounted on the ALSEP (Apollo Lunar Surface Experiments Package) central station. The Dust Detector was carried on Apollo's 11, 12, 14 and 15. The Apollo 11 DTREM was powered by solar cells and only operated for a few months as planned. The Apollo 12, 14, and 15 detectors operated for 5 to 7 years, returning data every 54 seconds, consisting of voltage outputs from the three solar cells and temperatures measured by the three thermistors. The telemetry was received at ground stations and held on the Apollo Housekeeping (known as "Word 33") tapes. made available to the National Space Science Data Center (NSSDC) by Yosio Nakamura (University of Texas Institute for Geophysics). We have converted selected parts of the telemetry into uncalibrated and calibrated output voltages and temperatures.

McBride, M. J.↗

NASA NTRS2012

Restoration of APOLLO Data by the NSSDC and PDS Lunar Data Node

The Apollo Lunar Surface Experiment Packages (ALSEPs), suites of instruments deployed by the Apollo 12. 14, 15, 16 and 17 astronauts on the lunar surface, still represent the only in-situ measurements of the Moon's environment taken over long time periods, Much of these data are housed at the National Space Science Data Center (NSSDC) at Goddard Space Flight Center but are in forms that are not readily usable, such as microfilm, hardcopy, and magnetic tapes with older, obsolete formats. The Lunar Data Node (LDN) has been formed under the auspices of the Planetary Data System (PDS) Geosciences Node to put relevant, scientifically important Apollo data into accessible digital form for use by researchers and mission planners. The LDN has prioritized the restoration of these data based on their scientific and engineering value and the level of effort required. We will report on progress made and plans for future data restorations.

Williams, David R.↗

NASA NTRS2011

Restoration of Apollo Data by the NSSDC and the PDS Lunar Data Node

The Lunar Data Node (LDN), under the auspices of the Geosciences Node of the Planetary Data System (PDS), is restoring Apollo data archived at the National Space Science Data Center. The Apollo data were arch ived on older media (7 -track tapes. microfilm, microfiche) and in ob solete digital formats, which limits use of the data. The LDN is maki ng these data accessible by restoring them to standard formats and archiving them through PDS. The restoration involves reading the older m edia, collecting supporting data (metadata), deciphering and understa nding the data, and organizing into a data set. The data undergo a pe er review before archive at PDS. We will give an update on last year' s work. We have scanned notebooks from Otto Berg, P.1. for the Lunar Ejecta and Meteorites Experiment. These notebooks contain information on the data and calibration coefficients which we hope to be able to use to restore the raw data into a usable archive. We have scanned Ap ollo 14 and 15 Dust Detector data from microfilm and are in the proce ss of archiving thc scans with PDS. We are also restoring raw dust de tector data from magnetic tape supplied by Yosio Nakamura (UT Austin) . Seiichi Nagihara (Texas Tech Univ.) and others in cooperation with NSSDC are recovering ARCSAV tapes (tapes containing raw data streams from all the ALSEP instruments). We will be preparing these data for archive with PDS. We are also in the process of recovering and archivi ng data not previously archived, from the Apollo 16 Gamma Ray Spectro meter and the Apollo 17 Infrared Spectrometer.

Williams, David R.↗

NASA NTRS2011

Lunar Surface Electric Potential Changes Associated with Traversals through the Earth's Foreshock

We report an analysis of one year of Suprathermal Ion Detector Experiment (SIDE) Total Ion Detector (TID) resonance events observed between January 1972 and January 1973. The study includes only those events during which upstream solar wind conditions were readily available. The analysis shows that these events are associated with lunar traversals through the dawn flank of the terrestrial magnetospheric bow shock. We propose that the events result from an increase in lunar surface electric potential effected by secondary electron emission due to primary electrons in the Earth's foreshock region (although primary ions may play a role as well). This work establishes (1) the lunar surface potential changes as the Moon moves through the terrestrial bow shock, (2) the lunar surface achieves potentials in the upstream foreshock region that differ from those in the downstream magnetosheath region, (3) these differences can be explained by the presence of energetic electron beams in the upstream foreshock region and (4) if this explanation is correct, the location of the Moon with respect to the terrestrial bow shock influences lunar surface potential.

Collier, Michael R.↗

NASA NTRS2010

PDS Lunar Data Node Restoration of Apollo In-Situ Surface Data

The Apollo missions between 1969 and 1972 deployed scientific instruments on the Moon's surface which made in-situ measurements of the lunar environment. Apollo II had the short-term Early Apollo Surface Experiments Package (EASEP) and Apollos 12, 14, 15, 16, and 17 each set up an Apollo Lunar Surface Experiments Package (ALSEP). Each ALSEP package contained a different suite of instruments which took measurements and radioed the results back to Earth over periods from 5 to 7 years until they were turned off on 30 September 1977. To this day the ALSEP data remain the only long-term in-situ information on the Moon's surface environment. The Lunar Data Node (LDN) has been formed under the auspices of the Planetary Data System (PDS) Geosciences Node to put relevant, scientifically important Apollo data into accessible digital form for use by researchers and mission planners. We will report on progress made since last year and plans for future data restorations.

Williams, David R.↗

NASA NTRS2009

Lunar Surface Potential Increases during Terrestrial Bow Shock Traversals

Since the Apollo era the electric potential of the Moon has been a subject of interest and debate. Deployed by three Apollo missions, Apollo 12, Apollo 14 and Apollo 15, the Suprathermal Ion Detector Experiment (SIDE) determined the sunlit lunar surface potential to be about +10 Volts using the energy spectra of lunar ionospheric thermal ions accelerated toward the Moon. We present an analysis of Apollo 14 SIDE "resonance" events that indicate the lunar surface potential increases when the Moon traverses the dawn bow shock. By analyzing Wind spacecraft crossings of the terrestrial bow shock at approximately this location and employing current balancing models of the lunar surface, we suggest causes for the increasing potential. Determining the origin of this phenomenon will improve our ability to predict the lunar surface potential in support of human exploration as well as provide models for the behavior of other airless bodies when they traverse similar features such as interplanetary shocks, both of which are goals of the NASA Lunar Science Institute's Dynamic Response of the Environment At the Moon (DREAM) team.

Collier, Michael R.↗

NASA NTRS2008

The Lunar Potential Determination Using Apollo-Era Data and Modern Measurements and Models

Since the Apollo era the electric potential of the Moon has been a subject of interest and debate. Deployed by three Apollo missions, Apollo 12, Apollo 14 and Apollo 15, the Suprathermal Ion Detector Experiment (SIDE) determined the sunlit lunar surface potential to be about +10 Volts using the energy spectra of lunar ionospheric thermal ions accelerated toward the Moon. More recently, the Lunar Prospector (LP) Electron Reflectometer used electron distributions to infer negative lunar surface potentials, primarily in shadow. We will present initial results from a study to combine lunar surface potential measurements from both SIDE and the LP/Electron Reflectometer to calibrate an advanced model of lunar surface charging which includes effects from the plasma environment, photoemission, secondaries ejected by ion impact onto the lunar surface, and the lunar wake created downstream by the solar wind-lunar interaction.

Collier, Michael R.↗

NASA NTRS2004

Automated Processing of ISIS Topside Ionograms into Electron Density Profiles

Modeling of the topside ionosphere has for the most part relied on just a few years of data from topside sounder satellites. The widely used Bent et al. (1972) model, for example, is based on only 50,000 Alouette 1 profiles. The International Reference Ionosphere (IRI) (Bilitza, 1990, 2001) uses an analytical description of the graphs and tables provided by Bent et al. (1972). The Alouette 1, 2 and ISIS 1, 2 topside sounder satellites of the sixties and seventies were ahead of their times in terms of the sheer volume of data obtained and in terms of the computer and software requirements for data analysis. As a result, only a small percentage of the collected topside ionograms was converted into electron density profiles. Recently, a NASA-funded data restoration project has undertaken and is continuing the process of digitizing the Alouette/ISIS ionograms from the analog 7-track tapes. Our project involves the automated processing of these digital ionograms into electron density profiles. The project accomplished a set of important goals that will have a major impact on understanding and modeling of the topside ionosphere: (1) The TOPside Ionogram Scaling and True height inversion (TOPIST) software was developed for the automated scaling and inversion of topside ionograms. (2) The TOPIST software was applied to the over 300,000 ISIS-2 topside ionograms that had been digitized in the fkamework of a separate AISRP project (PI: R.F. Benson). (3) The new TOPIST-produced database of global electron density profiles for the topside ionosphere were made publicly available through NASA s National Space Science Data Center (NSSDC) ftp archive at . (4) Earlier Alouette 1,2 and ISIS 1, 2 data sets of electron density profiles from manual scaling of selected sets of ionograms were converted fiom a highly-compressed binary format into a user-friendly ASCII format and made publicly available through nssdcftp.gsfc.nasa.gov. The new database for the topside ionosphere established as a result of this project, has stimulated a multitude of new studies directed towards a better description and prediction of the topside ionosphere. Marinov et al. (2004) developed a new model for the upper ion transition height (Oxygen to Hydrogen and Helium) and Bilitza (2004) deduced a correction term for the I N topside electron density model. Kutiev et al. (2005) used this data to develop a new model for the topside ionosphere scale height (TISH) as a function of month, local time, latitude, longitude and solar flux F10.7. Comparisons by Belehaki et al. (2005) show that TISH is in general agreement with scale heights deduced from ground ionosondes but the model predicts post-midnight and afternoon maxima whereas the ionosonde data show a noon maximum. Webb and Benson (2005) reported on their effort to deduce changes in the plasma temperature and ion composition from changes in the topside electron density profile as recorded by topside sounders. Limitations and possible improvements of the IRI topside model were discussed by Coisson et al. (2005) including also the possible use of the NeQuick model, Our project progressed in close collaboration and coordination with the GSFC team involved in the ISIS digitization effort. The digitization project was highly successful producing a large amount of digital topside ionograms. Several no-cost extensions of the TOPIST project were necessary to keep up with the pace and volume of the digitization effort.

Reinisch, bodo W.↗

NASA NTRS1988

Data Catalog Series for Space Science and Applications Flight Missions: Descriptions of Data Sets from Geostationary and High-Altitude Scientific Spacecraft and Investigations - Volume 2B

The main purpose of the data catalog series is to provide descriptive references to data generated by space science flight missions. The data sets described include all of the actual holdings of the Space Science Data Center (NSSDC), all data sets for which direct contact information is available, and some data collections held and serviced by foreign investigators, NASA and other U.S. government agencies. This volume contains narrative descriptions of data sets from geostationary and high altitude scientific spacecraft and investigations. The following spacecraft series are included: Mariner, Pioneer, Pioneer Venus, Venera, Viking, Voyager, and Helios. Separate indexes to the planetary and interplanetary missions are also provided.

Schofield, Norman J.↗