A version known as Blue Silk with lower top-speed limits was used in some marks of Canberra and Royal Navy aircraft.
This called for a device to provide an accurate measure of the groundspeed of an aircraft to within 0.2 percent while flying at any speed between 100 and 700 knots at all altitudes up to 60,000 feet.
[2] The solution to measuring ground speed was already well understood at the time, using a Doppler radar system to compare the returned frequency of two or more signals.
Green Satin used four such signals to determine both ground speed and drift angle, which were sent out simultaneously by a single cross-shaped antenna with feed horns at the four ends.
To measure the angle, the entire antenna array was mounted on a motorized pivot and rotated back and forth until the output was zero again.
[4] The electronics were housed within two pressurized canisters mounted on large backplanes that included power supplies and various electrical connections.
Data from the Green Satin was fed into the Navigation and Bombing System (NBS), a mechanical computer that calculated the current location of the aircraft through the continual dead reckoning of the inputs.
[3] In order to determine the operational accuracy of Green Satin, a lengthy series of test flights over land and water were carried out from an early Canberra.
[5] Accurate heading information was supplied by the Azimuth Datum Instrument (ADI), a star tracker mounted on a periscope so that it projected its display on a plate in front of the navigator.
For initial position fixes, Gee was replaced with the Decca Navigator System (Mark 6), which directly output measurements on three dials.
[8] Testing demonstrated that accuracy of Green Satin over land in straight and level flight was less than ±0.1% of distance flown, and less than ±0.1 of a degree in drift.
[9] The Green Satin was initially used with a simple display system with two large dials presenting true ground speed in knots on the left, and drift angle on the right.
The GPI was a simple mechanical computer that integrated the inputs to produce an offset from a user-provided initial location (taken from Gee, for instance), and presented this as either latitude and longitude or grid reference numbers on two odometer-like displays.
Problems locking on to a calm sea surface meant Decca navigational equipment had to be used instead during Grapple bomb aiming from Valiant aircraft.
With the scanning motor turned off, the display on the CRT was a single line, modulated in brightness by the returns at various distances from the aircraft.