PARCAE (NOSS)

PARCAE / NOSS

When the POPPY program was nearing its end, the Naval Research Lab designed a follow-up low-earth orbit ELINT satellite system under the name PARCAE. The primary mission was to locate, identify and track radar systems of Soviet naval vessels. Each PARCAE mission launched a cluster of three satellites on an Atlas booster into an almost circular orbit of about 1100 km altitude and an inclination of 63°. After the satellites had been released from the common carrier (named MSD - Multiple Satellite Dispenser), they separated to form a triangular pattern, which a side length of 30-120 km. This way, locations of radar emitters could be determined by triangulating the signal source. The first two triplets of PARCAE satellites were built by the NRL, after which production was taken over by Martin Marietta.

Image: NRO

PARCAE

The NRO mission numbering continued the Mission 7100 series of the POPPY program. The numerical program designator for PARCAE, if any, is unknown. The cover name "White Cloud" is sometimes mentioned, and before some basic facts incl. the PARCAE name had been declassified in 2023, the system has usually been referred to as NOSS (Naval Ocean Surveillance System). Just as for POPPY, the NSA had the task to analyze the ELINT data returned by PARCAE. The mission lifetime of a PARCAE triplet is unknown, but was most likely in the order of several years.

PARCAE Launch List

• No.: Sequential flight number for the PARCAE program
• NRL PL: Naval Research Lab Payload numbers
• Name: Unclassified name of the satellite. The OPS number ("OPS" standing for "Operations") is a random number given to all military-related satellite launches between 1963 and May 1984. Since June 1984, U.S. military satellites get a sequential "USA" number. The OPS number was assigned per launch, while the USA number is assigned per satellite.
• Mission: Each mission had a unique NRO Mission number in the 71xx range, continuing the series of POPPY missions.
• COSPAR ID: International designation of the satellite

PARCAE launches

"Improved PARCAE" / NOSS-2

Beginning with the 10th mission, the PARCAE satellites were of a new and presumably larger/heavier design. This can be inferred by the use of the much more powerful Titan IV launch vehicle. Originally, they were designed to be launched with the Space Shuttle, but this launch option was no longer valid after the Shuttle had been grounded after the Challenger disaster in 1986. Any details about the upgrades compared to the original PARCAE series are still classified. As a secondary mission, the satellite dispenser module placed itself into an elliptical 1100 km × 9000 km orbit, and acted as a UHF communications link called SLDCOM (Satellite Launch Dispenser Communications System).

It is unknown, if the PARCAE satellites of this enlarged design had any specific name. The NRO referred to them as "Improved PARCAE" in its declassification statement, while the term NOSS-2 has been used in the open literature before that. Using data from amateur observers, the mission lifetime of an "Improved PARCAE" triplet can be estimated to be around 10 years.

"Improved PARCAE" Launch List

• No.: Sequential flight number for the PARCAE program
• Name: Unclassified name of the satellite. Since June 1984, U.S. military satellites get a sequential "USA" number.
• Mission: Each mission had a unique NRO Mission number in the 71xx range, continuing the series of the first-generation PARCAE missions.
• COSPAR ID: International designation of the satellite

"Improved PARCAE" launches

NOSS-3

The follow-up system to "Improved PARCAE" began to launch satellites in 2001, and is still classified. The association of 8 launches between September 2001 and March 2017 with PARCAE / NOSS could be deduced by the satellites' orbits, which is also a roughly circular one at 1100 km altitude and an inclination of 63°. Officially, the launches put only one working satellite in orbit, with a second component officially listed as "debris". But from observations, it became clear that the alleged debris must also be a functioning satellite. The NOSS-3 satellites were launched with Atlas launch vehicles of various subtypes. The fourth mission, NROL-30, suffered from a partial launch failure, when the Centaur upper stage burn ended prematurely, leaving the payload in a too low orbit. The satellites used their own maneuvering propulsion to correct the orbit, which shortened the overall mission lifetime.

There is no confirmed name for this series of satellites, which is usually referred to public sources as NOSS-3 (following on from the NOSS-2 label for the "Improved PARCAE" series). It is possible, that the name INTRUDER is associated with the NOSS-3 satellites and/or the overall program. NRO Mission numbers are also unknown.

NOSS-3 Launch List

• No.: Sequential flight number for the NOSS-3 program
• Name: Unclassified name of the satellite. Since June 1984, U.S. military satellites get a sequential "USA" number. The name refers to the first satellite of each pair, with the COSPAR ID ending in "A". The second satellites are all officially catalogued as "debris".
  "NROL" stands for National Reconnaissance Office Launch, a number assigned by the NRO to its satellite launches since 1996.
• COSPAR ID: International designation of the satellite.

NOSS-3 launches

NOSS-4(?)

There are two NRO launches, which each placed a single satellite in an orbit with the typical NOSS parameters. Because of their orbits, these satellites are listed as "NOSS-4" in several listings of U.S. military satellites. The actual mission, and exactly how they are related to the earlier NOSS-3 series, is effectively unknown, though.

Launches possibly related to NOSS

Main Sources

[1] PARCAE, America's Ears in Space, NRO, 2023
[2] Gunter Krebs: Gunter's Space Page (for launch lists)

Back to Directory of U.S. Military Rockets and Missiles, Appendix 3

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Last Updated: 15 July 2025