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Spacecraft designers are driving observatories to the distant Sun-Earth Lagrange Point 2 (SEL2) to meet ever-increasing
science requirements. The mass fraction dedicated to propellant for these observatories to reach and operate at SEL2
will be allocated with the upmost care, as it comes at the expense of optics and instrument masses. As such, these
observatories could benefit from on-orbit refueling, allowing greater dry-to-wet mass ratio at launch and/or longer
mission life.
NASA is developing technologies, capabilities and integrated mission designs for multiple servicing applications in low
Earth orbit (LEO), geosynchronous Earth orbit (GEO) and cisluner locations. Restore-L, a mission officially in
formulation, will launch a free-flying robotic servicer to refuel a government-owned satellite in LEO by mid 2020.
This paper will detail the results of a point design mission study to extend Restore-L servicing technologies from LEO
to SEL2. This SEL2 mission would launch an autonomous, robotic servicer spacecraft equipped to extend the life of two
space assets through refueling. Two space platforms were chosen to 1) drive the requirements for achieving SEL2 orbit
and rendezvous with a spacecraft, and 2) to drive the requirements to translate within SEL2 to conduct a follow-on
servicing mission. Two fuels, xenon and hydrazine, were selected to assess a multiple delivery system. This paper will
address key mission drivers, such as servicer autonomy (necessitated due to communications latency at L2). Also
discussed will be the value of adding cooperative servicing elements to the client observatories to reduce mission risk.
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