The radiation experiments confirmed that the design of Apollo hardware would protect the astronauts from average and greater-than-average short-term exposure to solar particle events.The micrometeoroid experiments recorded 22 impacts showing the average micrometeoroid flux near the Moon was about two orders of magnitude greater than in interplanetary space but slightly less than in the near-Earth environment.Altogether the Orbiters returned 2,180 high resolution and 882 medium resolution frames. These 5 Lunar Orbiters which returned photography of 99% of the surface of the Moon (near and far side) with resolution down to 1 meter.The Lunar Orbiter program was managed by NASA Langley Research Center and involved building and launching 5 spacecraft to the Moon at a total cost of $163 million. Related: The spectacular Earthrise as seen from the Moon by the Soviet Zond 7 spacecraft Lunar Orbiter Program Deorbiting prevented interference with future Lunar Orbiter spacecraft. On October 29, with the spacecraft’s systems deteriorating and its fuel tanks nearly empty, ground controllers commanded Lunar Orbiter 1 to fire its engine to crash it onto the Moon on its 577th orbit. When its photography mission was completed, it continued to return radiation, micrometeoroid, and engineering data, and tracking of its orbit enabled a preliminary understanding of mass concentrations, or mascons, on the Moon that over time perturbed the spacecraft’s trajectory. The spacecraft photographed all the planned potential Apollo landing sites, returning the highest resolution images of the Moon’s near and far sides to that time. It took its last photograph of the Moon on August 28. Until September 16, Lunar Orbiter 1 transferred a total of 229 images of the Moon (42 high-resolution and 187 medium-resolution photos) to the Earth. This version was released by NASA in 2008. Laser Altimetry Lunar Reconnaissance Orbiter Moon Orbit Determination Radio Tracking.The reprocessed version of The first photograph of Earth from the Moon’s orbit. LROC NAC images also provide independent accuracy estimation, through the repeated views taken of anthropogenic features for instance. Comparisons with the radio-only orbits are used to evaluate this new tracking type, of interest for the OD of future lunar orbiters carrying a laser altimeter. We extend the 'direct altimetry' technique developed for the ICESat mission to perform OD and adjust spacecraft position to minimize discrepancies between LOLA tracks and SLDEM2015. With SLDEM2015 (a combination of the LOLA topographic profiles and the Kaguya Terrain Camera stereo images), another use of altimetry is possible for OD. In particular, the LOLA altimetric data give accurate, uniform, and independent information about LRO's orbit, with a different sensitivity and geometry which includes coverage over the lunar farside and is not tied to ground-based assets. We describe modeling improvements and the use of new measurements. Here, we report on the status of the OD effort since the beginning of the mission, a period spanning more than seven years. One-way tracking through Laser Ranging can supplement the tracking available for OD with 28-Hz ranges with 20-cm single-shot precision, but is available only on the nearside (the lunar hemisphere facing the Earth due to tidal locking). However, orbit reconstruction is in part limited by the 0.3-0.5 mm/s measurement noise level in S-band tracking. The high-accuracy gravity fields from GRAIL, with <10 km spatial resolution, further improved the radio-only orbit reconstruction quality ( <10 meters). LRO-specific gravity field solutions were determined and allowed radio-only OD to perform at the level of 20 meters, although secular inclination changes required frequent updates. The initial position knowledge requirement (50 meters) was met with radio tracking from ground stations, after combination with LOLA altimetric crossovers. The high-resolution data acquired by LRO benefit from precise orbit determination (OD), limiting the need for geolocation and co-registration tasks. The Lunar Reconnaissance Orbiter (LRO) has been orbiting the Moon since 2009, obtaining unique and foundational datasets important to understanding the evolution of the Moon and the Solar System.
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