Spy Satellites, Nuclear Threats, and Radar Wars: Inside the Declassified Project Parcae
31st Jan 2025
Project Parcae, a classified US satellite programme, played a critical role in intelligence gathering during a tense period of global competition and remained classified for more than 30 years. The system provided the U.S. military with unique electronic eavesdropping capabilities during the Cold War, restoring the strategic military balance in space and on the ground.
The Hot Times Of The Cold War
In the 1970s, the Soviet Navy became a global maritime threat, and the United States lacked global ocean surveillance capabilities. Soviet Kirov-class cruisers, 28,000-tonne monsters armed with SS-N-19 nuclear missiles, could remain invisible to U.S. radar.
In 1971, during a secret exercise, the US realised that its existing spy satellites needed weeks to process data from Soviet ships. The Pentagon feared that the USSR, through these ships, could violate the MAD (Mutual Assured Destruction) doctrine. The answer to this problem was Project Parcae, a secret program to create a network of spy satellites that could monitor the radio emissions of Soviet ships in real time.
This programme was crucial for restoring military equilibrium and preventing geopolitical tensions from escalating into a nuclear confrontation between the two superpowers.
Satellite ELINT Dynasty
Parcae, also known informally as NOSS-2 (Naval Ocean Surveillance System), was the third Navy satellite ELINT programme funded by the NRO.
The first was a GRAB satellite, about as big as an exercise ball. GRAB stood for Galactic Radiation and Background Experiment, a cover name for the satellite’s secret payload; it also had a bona fide solar science payload housed in the same shell. On 22 June 1960, GRAB made it into orbit to become the world’s first spy satellite, though there was no opportunity to brag about it. The existence of GRAB’s classified mission was an official secret until 1998.

GRAB satellites tracked several thousand Soviet air defence radars scattered across the vast Russian continent, picking up radar pulses and transmitting them to ground stations in friendly countries worldwide.
In 1962, the GRAB programme was revised to more advanced satellites and renamed Poppy. This programme operated until 1977 and was partially declassified in 2004.
From December 1962 to August 1977, America launched seven satellites into space under the Poppy programme. Poppy’s average orbital lifetime was 34 months.
With several satellites in orbit, Poppy could detect and geolocate radar emissions from Soviet ships and ground systems. Still, until the latter stages of the programme, it could take weeks or more to make sense of its data.
Parcae: The Most Powerful Electronic Intelligence System In Orbit

The Parcae programme incorporated the experience and technology of previous systems. It was a constellation of passive electronic reconnaissance satellites that precisely located ships by triangulating their radar emissions.
The first Parcae launches used an Atlas F rocket to deliver three satellites in the precise orbital formations required for their geolocation and tracking functions. Further launches used the larger Titan IV-A rocket.
The triple launch capability was achieved using the MSD (Multiple Satellite Dispenser), which the NRL team designed and built.

In orbit, the three satellites separated from each other and flew together in a triangle shape. They had 10-15 metre-long gravity orientation booms that ensured that the side of the satellite body on which the signal antennas were mounted was permanently oriented towards Earth.
Using onboard low-thrust engines, the satellites maintained their target position as a group at 30 to 240 kilometres from each other. This satellite array determined the location of radio and radar transmitters using triangulation. The three satellites measured the arrival times of Soviet radar signals using clocks synchronised to the nearest nanosecond. Comparing the delays, they calculated the ship’s position with an error of 500 metres.
Ground-based processing of direction-finding data from target transmitter signals from a constellation of satellites and successive groups of satellites produced coordinates, direction, and speed.
Today, we would call it passive GPS, but unlike GPS, Parcae did not transmit anything: it listened.
The data was encrypted and sent through Tactical Receive Equipment, a secure protocol available only to submarines and naval commands. If the Kirov turned on the radar, the alarm came in record time.
Another innovation used to identify each ship by its radar fingerprint accurately was the HULTEC (Hull-to-Emitter Correlation) system. Developed by NRL, this system matched each signal to a specific hull. ‘Each radar had a unique ‘signature’, such as a regional accent,’ explains Hammarstrom. ‘The Kirov emitted different frequencies from the Delta submarine, and Parkae recognised them.’
The raw data was processed by SEL-810 computers that filtered millions of signals, extracting only the relevant ones.

The satellites allowed the U.S. Navy to get the exact coordinates of Soviet ships in just 300 seconds through ELINT antennas and atomic clocks. It was a true breakthrough, turning strategic intelligence into tactical intelligence.
‘It was like Google Maps for the Navy, but in the ‘70s,’ jokes Arthur Collier, a former project manager.
Who Created Parcae and How
The first two sets of satellites were manufactured by engineers at the Naval Research Laboratory (NRL) of Washington, DC, and their contractor partners at Systems Engineering Laboratories and HRB Singer, a signal analysis and processing firm in State College, Pennsylvania.
Satellite production was then transferred to Martin Marietta under the direction of the US Air Force Space and Missile Systems Organisation, with technical support from the Naval Research Laboratory.
The subsequent system used the more significant, improved Parace satellite triplets (NOSS-2).
The National Reconnaissance Office (NRO) coordinated the programme and its funding. Since its inception in 1961, the NRO has directed and controlled all national spy satellite programmes, including those for photographic reconnaissance, communications interception, electronic intelligence, and radar.
The NRO later developed the next generation of Parcae, called Improved Parcae, which added the ability to collect and recognise selected foreign communications systems
Parcae and Improved Parcae were Low Earth Orbit electronic intelligence collection systems that downlinked the collected data to ground processing facilities located at selected locations worldwide. Once received, the data was provided to the National Security Agency for processing and reporting to U.S. policymakers.
The first of Parcae’s 13 missions was launched on 30 April 1976, and the last on 12 May 1996.
All The Secrets Are Not Yet Revealed
For many years, the existence of Parcae has remained a mystery.
Over the years, a few enterprising journalists in venues such as Aviation Week & Space Technology and The Space Review, some historians, and even a Russian military advisor in a Ministry of Defence journal have unofficially exposed aspects of the Parcae programme.
It was not until July 2023 that the NRO director confirmed its existence by issuing a brief one-page statement with limited details.
Over the years, the programme has been known by various aliases such as White Cloud and Classic Wizard.
The Parcae programme was successfully operated by the NRO and discontinued in 2008. However, its legacy lives on today. The Tactical Receive Equipment communications system was adopted during the Gulf War to transmit satellite imagery in real-time. HULTEC correlation techniques are used in cybersecurity to identify hackers by their digital ‘fingerprints.’
Parcae’s principles inspire modern ELINT satellites such as those in the NROL-151 constellation (these, unlike Parcae, are still classified).
The experts who built and operated Parcae and those who relied on it for national security emphasise that much of the story is still classified and untold.
At the same time, the engineers who built the satellite system say they were not more professionally and creatively engaged before or after the programme.
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