NASA’s Goddard Space Flight Center is seeking sources to design, analyze, fabricate, and qualify three flight assemblies and one flight spare Frequency Reference System (FRS) for the Laser Interferometer Space Antenna (LISA) mission. Each unit includes an optical reference cavity and associated electronics, with environmental testing required. Targeted delivery dates are February 2029 for the first flight unit, September 2029 for the second, March 2030 for the third, and May 2030 for the spare. Performance of services is anticipated at the vendor’s facility, with virtual or on-site monthly status reviews. No budget amount is specified in the description.