In fiscal year 1965, the Nike-X Project Office was assigned a new mission -- the Nike-X Reentry Measurements Program, or RMP. Conducted at the Kwajalein Test Site in the Marshall Islands, the RMP was a joint program involving Advanced Research Projects Agency, or ARPA, Army, Navy and Air Force which sought "to expand the existing knowledge of ballistic reentry phenomena and discrimination criteria."In other words they were tasked to determine what could be seen which would define sensor techniques and to assess the relationship between the target types and the sensor measurements which would define the most effective discrimination techniques.Also with this basic data collection, scientists could then "extrapolate to other possible threat sizes and variations." As one text noted, "the program used a straightforward phenomenological approach, with tabulated comparisons of radar observable characteristics as functions of vehicle size, shape and ablator material."The Nike-X RMP soon became "a sizable effort" which would last through 1970. Target reentry was observed from the Eastern Test Range on the Atlantic Ocean and White Sands Missile Range, New Mexico, but most of the full scale reentry tests were flown into the Kwajalein Test Site. The program incorporated all of the available radar and sensor systems on Kwajalein to include the Discrimination Radar, the two Target Track Radars #4 and #5 which were modified for this role, and general range instrumentation support.From Roi-Namur, the Advanced Research Projects Agency's Project Press Tradex radar also participated in the test program. In addition, a special EC-121K optical aircraft provided data not available to ground-based sensors. Equipped with a special dome, the Lockheed Super-G Constellation aircraft, a converted Navy radar search plane, housed both optical and infrared sensors.The first phase -- RMP-A -- which was designed to collect data on target vehicles as they re-entered the earth's atmosphere, concluded June 30, 1966. These reentry studies focused specifically upon 'slick' conical vehicles. This area received the initial emphasis as this debris is more difficult to measure and discriminate because of "its reduced interaction with the atmosphere," particularly when compared to blunt vehicles.Planning for Phase B began with the end of Phase A in June 1966, to develop a 30-month program employing 17 launches from Vandenberg Air Force Base, California. Unlike the first phase, RMP-B introduced a variety of payloads of differing shapes, sizes and materials.In addition, a Sequential Payload Delivery system, developed by the Advanced Development Program, introduced a new capability. Boosted by an Atlas D, the new delivery system could eject primary re-entry vehicles, subscale re-entry vehicles, and secondary payloads such as chaff on a preprogrammed schedule, creating new opportunities for Kwajalein's sensors.The first launch occurred one year later on June 9, 1967. KX101, the first RMP-B flight, was also the first known flight of multiple independently targeted payloads on a single booster. In addition according to contemporaries, KX101 was "probably also the first successful flight of solid propellant start-stop and restart motor."Launched from Vandenberg Air Force Base, the first flight of the RMP-B consisted of three payloads. Equipped with the Sequential Payload Delivery System, or SPDS, the vehicle flew a preprogrammed flight path which enabled the SPDS to eject the three targets at 60 second intervals while ensuring that all three would pass through the same point in space. The goal was to determine what effects different sized and shaped reentry vehicles would have on the generated wake during reentry into the atmosphere. The launch operation and the delivery of all three payloads to Kwajalein were successful.Created in-house by the Advanced Development Program, the SPDS proved to be a most cost effective tool in the study of reentry phenomena. With 17 launches over a 30-month period, the RMP-B incorporated a series of specially developed reentry measurements vehicles, tactical offensive weapons with penetration aids, and vehicles developed for future offensive weapons.In addition to the NIKE-X, targets were provided by the Air Force Advanced Ballistic Reentry Systems Studies, Strategic Air Command Evaluation Missions, and the Navy's Polaris program. Thus, the resulting information obtained from this Nike-X RMP was used not only for the advanced development of the ballistic missile defense system but also in the development of other Department of Defense programs.