The Nation's Vision for Space Exploration calls for undertaking lunar exploration activities to enable sustained human and robotic exploration of Mars and beyond, including more distant destinations in the solar system. NASA's Science Mission Directorate (SMD) is charged with the establishment and implementation of a Robotic Lunar Exploration Program (RLEP); Goddard Space Flight Center (GSFC) has lead Center responsibility for managing and executing the program.
The Robotic Lunar Exploration Program (RLEP) is expected to execute a series of robotic missions to the Moon, starting in 2008, in order to pave the way for human exploration missions to the Moon and, ultimately, to Mars and beyond. The role of the RLEP is to ensure that all lunar flight missions are integrated into a program in a manner that allows them to achieve mission success, and support the larger goal of human exploration. For planning purposes, each flight mission is constrained to Discovery-class program resources (full cost, full lifecycle, including instruments, spacecraft, launch vehicle, ground systems, and mission operations), to be developed in less than four years. While the first flight mission will be purely orbital (i.e. the 2008 Lunar Reconnaissance Orbiter, hereafter LRO), subsequent missions may include surface elements (landed, or impacted), as required to best provide required measurements, validation of technologies, and risk mitigation for follow-on human missions. However, it is possible that each flight mission will include an orbital element, if for no other reason than to provide a platform for payload delivery and/or communications back to Earth.
One goal of RLEP is to provide an early assessment of human exploration targets on the Moon, followed by a risk mitigation strategy for both the technology developments needed for human exploration and the emplacement of supporting infrastructure. This will require a comprehensive, quantitative assessment of the character of the lunar surface (and shallow subsurface) environment in all regions deemed relevant to human exploration activities. Although much is known from the Apollo missions (and their predecessors), many factors still remain unanswered in terms of human health, safety, and performance, particularly for longer lunar surface stays and in association with lunar polar regions, where the potential for using water ice as a resource is a possibility. RLEP will first provide the observational data in the form of fully calibrated and validated measurements to help address these questions. It will then assist in meeting the challenges posed by human exploration technology maturation, as well as emplacement of the operations support infrastructure, both Moon- and Earth-based. RLEP will provide critical elements in support of all phases of the planned human exploration Program for the Moon, as a key step toward conducting human activities on Mars.
In order to keep pace with the evolving nature of the human exploration program, a mixed mode of flight missions is envisioned for RLEP. The Lunar Reconnaissance Orbiter (LRO) is a remote sensing orbiter planned for launch in 2008. While LRO is planned for a Delta-class launch vehicle and its associated performance capabilities, this is not necessarily the case for all the follow-on flight missions. Follow-on missions may include landers, both soft and hard, utilizing impactors and surface probes, and possibly systems with limited surface and sub-surface mobility. Other missions may include communications, ranging, and navigation satellites, as well as lunar surface and Earth ground assets that help achieve these capabilities. Also under consideration are small sub-satellites that could better define the gravitational field of the Moon, particularly on the far side. Other flight missions may be launched on a smaller Expendable Launch Vehicle (ELV) if their total mass is less than 400 kg. Such missions may support options for smaller probes, impactors, bio-sentinels, sub-satellites, and other technology demonstrators. NASA envisions a wide range of content and mission sizes and plans to seek community-based inputs to better define the range of cost-effective and fully-competed possibilities.
Larger scale missions (i.e. Discovery-class or larger) may support risk mitigation or infrastructure requirements originating from other elements of the Exploration Vision. The robotic emplacement of infrastructure may require that the infrastructure be developed externally to the RLEP program as a directed payload. The Exploration Program can utilize the quick response and relatively low cost of the RLEP to mitigate developmental risk on key manned flight system functions, such as automated rendezvous and docking, precision landing, or engine performance and control.
RLEP is unique in that as a program of multiple mission classes it can provide flexibility in both capability and response time that can be tailored to the individual Exploration Vision needs for specific measurements, technology demonstration/maturation efforts, and infrastructure emplacement. It is a program that will constantly be evolving, and unquestionably have a large content range. RLEP is intended to be an adaptable enabler of human exploration of the Moon as a key step to achieving the capability of sending humans to Mars.