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By © Charles P. Vick 2007 All Rights Reserved

07-14-15 ,-07

INDIGO – RADAR IMINT Spacecraft Series – (NRO/CIA/NSA Technology Demonstration Program leading to LACROSSE)

Code name INDIGO was the first in a series of earth orbit NRO/CIA/NSA, RADAR IMINT (radar imaging intelligence) spacecraft used by the CIA and intelligence Community for a variety of mission. They were launched by the Titan-23B Agena-D booster with a total of one launch. INDIGO which was an early CIA prototype of a radar imaging satellite. George H.W. Bush approved $250 million for two radar imaging satellite systems as Director of Central Intelligence in 1988. The CIA had planned to put imaging radar on an advanced KH-11, but Defense Secretary Harold Brown vetoed the idea because it would place too many assets on a single platform. The project was later merged with LACROSSE. (Richelson, J. " America 's Secret Eyes in Space." Harper and Row: New York. 1990. page 219.) The spacecraft were actually nothing more than a CIA technology demonstration program of a sophisticated earth orbit space based earth radar imaging station. The INDIGO introduced the first large deployable white gold mesh covered receiving radar dish antenna design of about 25-28 feet in diameter. The INDIGO was a radar imaging satellite technology demonstration leading to the LACROSSE radar imaging spacecraft. It only launch was on January 21, 1982 with an estimated mass of 7,950 pounds. It was designed to provide images of the earth surface through clouds which normally obstruct most photo imaging spacecraft via it synthetic aperture radar microwave imaging system. This capability to image through clouds also gave it the ability to image ground targets of interest at night as well as in daylight. Presumable the radars calibration took some weeks before the imaging in earnest was started. The technology for this radar imaging spacecraft was slow developed but proved out highly successfully once the technology was perfected. Like any new technology program it had its issues that slowed its initial progress.

The gravity gradient stabilized spacecraft was about 25-28 feet in diameter and about 42-44 feet long with the radar dish attached to gimbals for steering from the command, communication, control and intelligence, power bus attached to the Agena-D stage. INDIGO’s dish did not cover the entire visible surface of the earth and thus the dishes were presumable set on gimbals to monitor specific points or objects of interest.

It is presumed that the spacecraft bus carried the standard Agena-D two solar arrays and one down link communications dish. The launch shroud was 10 feet in diameter with a total length of 58 feet. This spacecraft utilized the five foot diameter by 20.86 foot long Agena-D based stage to place it on a 347.98 mile perigee by 400.18 mile apogee orbit at an inclination of 97.3 degrees with a spacecraft life of 122 days. The CIA primarily utilized it for earth imaging experiments as well as practical real imaging of primary points of interest. The Agena-D rocket stage portion of the satellite packages carried the usual assortment of earth, horizon and solar sensors to orient the spacecraft to air the spacecraft downward towards the earth for its imaging mission. The spacecraft was able to receive and send the data to several global ground stations via radio signal operated by NSA/CIA personnel. The data was then processed and analyzed at NSA headquarters for further analysis distribution to the CIA and interested intelligence community.


1. McDowell, Jonathan, U. S. Reconnaissance Satellites Programs, Part 1: Photoreconnaissance, Quest, Vol. 4, No. 2, Summer, 1995, pp.22-33.


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