Deriving the ancient lunar pole path from impact induced gravity anomalies

<p>The large anomalies in the lunar gravity field are in most cases the result of large impacts that occurred more than 3 billion years ago.  Today those anomalies provide the stability of the lunar rotation and if removed would cause a change in the position of the intersection of the spin pole with the lithosphere. Thus, extracting a gravity anomaly from today’s gravity field can provide the approximate location of the pole of rotation prior to the impact that caused the anomaly.  By removing the gravity field of each anomaly in order of age, youngest first, we can estimate the path of the lunar pole back 3 to 4 billion years, to the beginning of the time of heavy bombardment.</p><p>Starting from the GRAIL gravity model we selectively remove large gravity anomalies by first determining the center and dimensions of the anomaly from the Bouguer gravity and then deriving the average free air gravity for the Bouguer location and dimensions. The anomaly field is expanded into spherical harmonics and the degree 2 terms used to derive the change in pole position caused by the anomaly. Removing each anomaly in order of increasing age provides an estimate of the pole path from before the time of the first anomaly, SP-A.  Since the pole path depends on the order of the gravity anomalies being created it is important to know when each impact induced anomaly occurred.  The results suggest the re-constructed motion of the lunar pole of rotation is within approximately 10 dgerees of the present pole.</p>

Global database of direct solar radiation at the Moon’s surface for lunar engineering purposes

The purpose of this paper was to provide preliminary data concerning global availability of solar energy at the surface of the Moon. Lack of gaseous atmosphere and accompanying phenomena such as precipitations or cloud cover makes the Moon’s surface an extraordinarily advantageous place for solar energy harvesting. On the other hand, excessive exposure to undamped sunlight may cause problems with buildings’ interior overheating or increase decay rate of photovoltaic cells. Thus, basic information concerning solar irradiance and diurnal insolation at specified selenographic latitudes are indispensable for location selection for future lunar facilities and their design process. In order to approximate Sun’s position at lunar sky, simple analytical astrometric model of lunar rotation was developed. Basing on that model, direct diurnal irradiances and insolations were calculated for various flat surface orientations, and selenographic latitudes. Computed data were presented in charts and tables.This lunar insolation database may serve as guideline for location of future lunar settlements and research stations, and to estimate their diurnal energy demands.

Lunar Libration Tables and Determination of Crater Coordinates

The study of lunar rotation has attracted considerable interest with the advent of the epoch of exploration of the Solar system by space technology. A series of works on an investigation of the lunar gravitational field carried out with the help of artificial lunar satellites have greatly advanced our possibility for that study. The problem concerning the landing on the lunar surface of spacecraft, and the creation of durable lunar bases, impose heavy demands on the accuracy of theoretical description of orbital and rotational motion of the Moon.The development of the observational technology with the help of radio-and laser ranging (LLR) provides at the present time measurements of the distance to a given point on the Moon with an accuracy of about 2 cm, probably improved in the future to about 5mm (Banerdt, 1995). By using differential VLBI measurement with extragalactic radio sources angularly near the Moon, it should be possible to obtain routine estimates of angular position of the beacon to 0.1 mas from each observation (Baudry, 1995). Therefore, combining VLBI and LLR techniques will provide a means of achieving new objectives, and that calls for the development of the theories adequate to an accuracy for observations.