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The results of observations of the moon and planets are presented and include: (1) data on the discovery of high porosity values and the broken terrain of the lunar surface, and (2) data on the coloration of lunar rocks. A comparative description is given of data obtained by astronomical and by satellite observations.
In order to observe the lunar sodium exosphere out to one-half degree around the Moon, we designed, built and installed a small robotically controlled coronagraph at the Winer Observatory in Sonoita, Arizona. Observations are obtained remotely every available clear night from our home base at Goddard Space Flight Centeror from Prescott, Arizona. We employ an Andover temperature-controlled 1.5 Å wide narrow-band filter centered on the sodium D2line, and a similar 1.5 Å filter centered blueward of the D2line by 3Åfor continuum observations. Our data encompass lunations in 2015, 2016, and 2017, thus we have a long baseline of sodium exospheric calibrated images. During the course of three years we have refined the observational sequence in many respects. Therefore this paper only presents the results of the spring, 2017, observing season. We present limb profiles from the south pole to the north pole for many lunar phases.Our data do not fit any power of cosine model as a function of lunar phase or with latitude. The extended Na exosphere has a characteristic temperature of about 2250 -6750 K, indicative of a partially escaping exosphere. The hot escaping component may be indicative of a mixture of impact vaporization and a sputtered component.
We observed the 2019 January total lunar eclipse with the Hubble Space Telescope’s STIS spectrograph to obtain the first near-UV (1700–3200 Å) observation of Earth as a transiting exoplanet. The observatories and instruments that will be able to perform transmission spectroscopy of exo-Earths are beginning to be planned, and characterizing the transmission spectrum of Earth is vital to ensuring that key spectral features (e.g., ozone, or O3) are appropriately captured in mission concept studies. O3 is photochemically produced from O2, a product of the dominant metabolism on Earth today, and it will be sought in future observations as critical evidence for life on exoplanets. Ground-based observations of lunar eclipses have provided the Earth’s transmission spectrum at optical and near-IR wavelengths, but the strongest O3 signatures are in the near-UV. We describe the observations and methods used to extract a transmission spectrum from Hubble lunar eclipse spectra, and identify spectral features of O3 and Rayleigh scattering in the 3000–5500 Å region in Earth’s transmission spectrum by comparing to Earth models that include refraction effects in the terrestrial atmosphere during a lunar eclipse. Our near-UV spectra are featureless, a consequence of missing the narrow time span during the eclipse when near-UV sunlight is not completely attenuated through Earth’s atmosphere due to extremely strong O3 absorption and when sunlight is transmitted to the lunar surface at altitudes where it passes through the O3 layer rather than above it.
In order to observe the lunar sodium exosphere out to one-half degree around the Moon, we designed, built and installed a small robotically controlled coronagraph at the Winer Observatory in Sonoita, Arizona. Observations are obtained remotely every available clear night from our home base at Goddard Space Flight Center or from Prescott, Arizona. We employ an Andover temperature-controlled 1.5-angstrom-wide narrow-band filter centered on the sodium D2 line, and a similar 1.5-angstrom filter centered blueward of the D2 line by 3 angstroms for continuum observations. Our data encompass lunations in 2015, 2016, and 2017, thus we have a long baseline of sodium exospheric calibrated images. During the course of three years we have refined the observational sequence in many respects. Therefore this paper only presents the results of the spring, 2017, observing season. We present limb profiles from the south pole to the north pole for many lunar phases. Our data do not fit any power of cosine model as a function of lunar phase or with latitude. The extended Na exosphere has a characteristic temperature of about 2250–6750 degrees Kelvin, indicative of a partially escaping exosphere. The hot escaping component may be indicative of a mixture of impact vaporization and a sputtered component.
Determination of the depths of more than 1900 small lunar craters from measures of shadows on the long-focus pictures obtained by Lunar Orbiter IV. The method for converting the measured shadow length into the true length in nature of the shadow hypotenuse is new and is applicable to other planetary bodies, provided that comparable spacecraft ephemerides are available. The measures were made with a simple surveyor's plotting scale on the standard Orbiter IV photographic enlargements. The results indicate that the smaller lunar (D less than 30 km) crater are appreciably deeper than is indicated by earlier work using imagery obtained at terrestrial observatories.
The Moon is an excellent site for astronomical observations. This paper describes two geological aspects related to astronomy from the Moon. First it evaluates the sources of gases near a lunar base as input to calculations reported in a separate paper on the growth of an artificial lunar atmosphere. The results suggest that mining for He-3 could produce the most gas (1 kg/sec), but rocket exhaust (0.1 kg/sec) and habitat venting (0.5 kg/sec) are also important. Second, the paper discusses criteria that need to be considered when determining the site of a lunar astronomical facility. These are longitude and latitude (equatorial sites are favored), topography (important to be relatively flat for ease of installation), distance from a lunar base (to be free of seismic noise, dust, and gases), the site's value to lunar geoscience (other factors being equal, a geologically diverse site is better), and its value as a materials resource (mining and observatories are incompatible).
We observed the 2019 January total lunar eclipse with the Hubble Space Telescope’s STIS spectrograph to obtain the first near-UV (1700–3200 Å) observation of Earth as a transiting exoplanet. The observatories and instruments that will be able to perform transmission spectroscopy of exo-Earths are beginning to be planned, and characterizing the transmission spectrum of Earth is vital to ensuring that key spectral features (e.g., ozone, or O{sub 3}) are appropriately captured in mission concept studies. O{sub 3} is photochemically produced from O{sub 2}, a product of the dominant metabolism on Earth today, and it will be sought in future observations as critical evidence for life on exoplanets. Ground-based observations of lunar eclipses have provided the Earth’s transmission spectrum at optical and near-IR wavelengths, but the strongest O{sub 3} signatures are in the near-UV. We describe the observations and methods used to extract a transmission spectrum from Hubble lunar eclipse spectra, and identify spectral features of O{sub 3} and Rayleigh scattering in the 3000–5500 Å region in Earth’s transmission spectrum by comparing to Earth models that include refraction effects in the terrestrial atmosphere during a lunar eclipse. Our near-UV spectra are featureless, a consequence of missing the narrow time span during the eclipse when near-UV sunlight is not completely attenuated through Earth’s atmosphere due to extremely strong O{sub 3} absorption and when sunlight is transmitted to the lunar surface at altitudes where it passes through the O{sub 3} layer rather than above it.
During the few days centered about new Moon, the lunar surface is optically hidden from Earth-based observers. However, the Moon still offers an observable: an extended sodium tail. The lunar sodium tail is the escaping "hot" component of a coma-like exosphere of sodium generated by photon-stimulated desorption, solar wind sputtering and meteoroid impact. Neutral sodium atoms escaping lunar gravity experience solar radiation pressure that drives them into the anti-solar direction forming a comet-like tail. During new Moon time, the geometry of the Sun, Moon and Earth is such that the anti-sunward sodium flux is perturbed by the terrestrial gravitational field resulting in its focusing into a dense core that extends beyond the Earth. An all-sky camera situated at the El Leoncito Observatory (CASLEO) in Argentina has been successfully imaging this tail through a sodium filter at each lunation since April 2006. This paper reports on the results of the brightness of the lunar sodium tail spanning 31 lunations between April 2006 and September 2008. Brightness variability trends are compared with both sporadic and shower meteor activity, solar wind proton energy flux and solar near ultra violet (NUV) patterns for possible correlations. Results suggest minimal variability in the brightness of the observed lunar sodium tail, generally uncorrelated with any single source, yet consistent with a multi-year period of minimal solar activity and non-intense meteoric fluxes.
The Workshop on the Concept of a Common Lunar Lander, which was held at the NASA Johnson Space Center on July 1 and 2, 1991, discussed potential payloads to be placed on the Moon by a common, generic, unmanned, vehicle beginning late in this decade. At this workshop, a variety of payloads were identified including a class of one-meter (and larger) optical telescopes to operate on the lunar surface. These telescopes for lunar-based astronomy are presented in an earlier section of this report. The purpose of this section is to suggest that these and other payloads for the Common Lunar Lander be used to facilitate technology development for the proposed 16-meter Aperture UV/Visible/IR Large Lunar Telescope (LLT) and a large optical aperture-synthesis instrument analogous to the Very Large Array of the National Radio Astronomy Observatory.
The catalog contains the observational results obtained by the Celescope Experiment during the first 16 months of operation of NASA's Orbiting Astronomical Observatory (OAO-2). It lists the results of the stellar observations, along with selected ground-based information obtained from the available literature. Lunar observations (Ahmad and Deutschman, 1972), as well as other analyses of the data, are being published as separate papers. These data are available in two forms: (1) magnetic tapes and the necessary utility programs for reading and printing the contents of the tapes; and (2) this catalog, transcribed from the magnetic-tape catalog. The magnetic tape version contains not only the compiled results but also the results of the individual observations from which these averaged data were compiled.
High resolution radar data for the lunar surface were acquired over 14 sites in June and November 1990 using the new 10 MHz data taking system at the Arecibo Observatory. The raw data collected for each site covers an area approximately 100 by 400 km and will be processed using delay-Doppler techniques into images of backscatter cross section with three fo four independent looks. All observations transmitted a circularly polarized signal and both senses of circular polarization were received containing the polarized and depolarized component of the backscatter signal. The relative power in these two polarizations provides useful information on properties of the surface, in particular surface roughness. The effort to date focused on the initial data analysis with new software written to perform a full synthetic aperture focusing on the raw radar data. This analysis will involve the use of complementary high resolution optical and topographic data sets to aid interpretation of surface scattering mechanisms.
Present and future technologies to facilitate lunar composition and resource assessment with applications to lunar surface construction are presented. We are particularly interested in the construction activity associated with lunar-based astronomy. We address, as an example, the use of ground-probing radar to help assess subsurface conditions at sites for observatories and other facilities.
In order to investigate the feasibility of ice deposits at the lunar south pole, we have integrated all relevant lunar polar data sets. These include illumination data, Arecibo ground-based monostatic radar data, newly processed Clementine bistatic radar data, and Lunar Prospector neutron spectrometer measurements. The possibility that the lunar poles harbor ice deposits has important implications not only as a natural resource for future human lunar activity but also as a record of inner solar system volatiles (e.g., comets and asteroids) over the past billion years or more. We find that the epithermal neutron flux anomalies, measured by Lunar Prospector, are coincident with permanently shadowed regions at the lunar south pole, particularly those associated with Shackleton crater. Furthermore, these areas also correlate with the beta=0 circular polarization ratio (CPR) enhancements revealed by new processing of Clementine bistatic radar echoes, which in turn are colocated with areas of anomalous high CPR observed by Arecibo Observatory on the lower, Sun-shadowed wall of Shackleton crater. Estimates of the extent of high CPR from Arecibo Observatory and Clementine bistatic radar data independently suggest that approximately 10 square kilometers of ice may be present on the inner Earth-facing wall of Shackleton crater. None of the experiments that obtained the data presented here were ideally suited for definitively identifying ice in lunar polar regions. By assessing the relative merits of all available data, we find that it is plausible that ice does occur in cold traps at the lunar south pole and that future missions with instruments specifically designed to investigate these anomalies are worthy.
The paper outlines two techniques used for determining the instrumental stray radiance from orbital results obtained with the Skylab white light coronagraph. The first technique employs images of the lunar disk made near the time of solar eclipse to compare the apparent contrasts of maria and highlands recorded by the coronograph with those of previous studies and then determine the magnitude of the stray radiance and its variation along a radius. The second method determines the azimuthal variation of the stray radiance by measuring the change in the net radiance of a point in the coronal images as the image is rotated.
This grant supports the core program in planetary astronomy at Caltech. The research includes observations in the IR, sub-mm, mm and cm wavelengths at national and Caltech observatories with a strong emphasis on integrating the observations with spacecraft data and with models of atmospheric structure, dynamics and chemistry. Muhleman's group made extensive observations of Saturn, Uranus and Neptune which are being interpreted in terms of deep atmospheric structures which are obvious in the 2 and 6 cm maps of Saturn and Uranus. The microwave measurements are one of the few sources of information below the 2 bar level. Goldreich is investigating the dynamics of narrow rings with postdoctoral fellow, Pierre-Yves Longaretti. Their work has focused on the role of collisional stresses on the precession of the rings, since the Voyager radio science results imply that the previous model based on the ring's self-gravity is not the entire story. In addition Borderies, Goldreich and Tremaine have completed an investigation of the dynamics of the Encke division in Saturn's A ring.
Multispectral images and near-infrared reflectance spectra were obtained for the Reiner Gamma Formation, a swirllike albedo and magnetic anomaly in the western portion of the lunar near side, as well as for nearby geologic units in Oceanus Procellarum, using the University of Hawaii 2.24-m telescope at the Mauna Kea Observatory. The spectra of the high albedo swirl material are closely matched by models incorporating 90-95 percent fresh mare basalt with 5-10 percent highlands debris.
Imaging spectroscopy of the lunar surface was carried out using a CCD spectrograph employed as an imaging spectrometer at the University of Hawaii 2.24-m telescope at Mauna Kea Observatory. A portion of the Humorum multiringed impact basin was observed, yielding an imaging spectroscopic dataset consisting of approximately 400,000 spectra covering the wavelength region 0.7-0.98 microns at a spectral resolution of 200 (lambda/Delta-lambda). Results of this analysis included (1) identifying craters and other explosures of highland material within the bounds of Mare Humorum, (2) identifying craters in the highlands adjacents to Mare Humorum that excavate buried mare basalt, and (3) identifying two spectral units in the highlands that likely represent compositional units. The region is shown to be extremely diverse spectrally and demonstrates the ability of imaging spectroscopy to enable a qualitative improvement in the ability to identify and map compositional units.