Keller, John - The Lunar Reconnaissance Orbiter – Highlights and Looking Forward

Abstract: 
The Lunar Reconnaissance Orbiter (LRO) has been orbiting the Moon for five years. LRO science teams have delivered > 500 TB of data to the PDS, including higher-level data products (maps, mosaics, derived products), creating the largest single data archive for any NASA planetary science mission. Now, nearing completion of its first Extended Science Mission (ESM), LRO has proposed a second ESM (ESM2) in order to make new measurements in support of newly defined science questions. In addition to new science, LRO supports additional objectives that only LRO can currently provide, including the identification of safe landing sites for future landed missions, measurements that address Strategic Knowledge Gaps (SKGs), and can serve as a data relay for farside landers/rovers. In its current quasi-stable orbital configuration (polar orbit, ~30 x 180 km) LRO is capable of remaining in orbit for at least eight more years.
LRO’s seven instrument teams have been highly productive. Recent highlights include the identification of LRO-era impact craters, bi-static measurements of potential polar ice deposits, the variability of volatiles at and near the surface, and the variability of exospheric species. These recent discoveries form the core of LROs new objectives for the proposed ESM2. An overarching theme for ESM2 is change – on the surface, beneath the surface, and in the exosphere. The next two years of LRO operations will be an ambitious program of lunar and planetary science that are directly linked to the current Decadal Survey. Examples of the science LRO will address with 2 additional years of operations are given here. Evidence suggests that water molecules migrate across the lunar surface, LRO’s ESM2 will characterize this water cycle on seasonal time scales with multiple instruments using innovative methods only recently validated. A surprising number of new impacts were recently detected. LRO will systematically survey these fresh impacts to determine their global abundance and the current flux of small meteorites while elucidating new information on impact dynamics. The thermal properties of the surface show unanticipated variability, particularly in the polar regions. We will employ new techniques to characterize the vertical as well as the horizontal structure of the regolith with never-before possible measurements. On the basis of innovative measurement approaches recently validated by LRO, a series of coordinated multi-sensor measurement campaigns will be used in ESM2 to address science questions associated with the Moon’s interaction with the dynamic space environment.
LRO continues to maximize its capabilities by operating in nadir and off-nadir modes. Off-nadir pointing has enabled new measurements by nearly all instruments and expands the range of science questions that LRO can address. For example, new off-nadir measurements by the LAMP instrument allow for a more detailed characterization of the exosphere. Also, off-nadir measurements by LROC, LAMP, and Diviner allow for broader phase angle coverage and thereby extends the photometric coverage of each instrument. These measurements are new to LRO and open up new avenues for understanding the Moon and airless bodies.