BOX 2-5 Space-Based Remote Sensing of Debris: An Example
In late 1987, NASA began work on a proposal to detect 1-mm to 1-cm debris in LEO with a space-based electro-optical sensor. The project was called ''Quicksat" because, to obtain a free rocket launch, the instrument had to be constructed rapidly. To obtain an expected detection rate (in a 500-km, sun-synchronous orbit) of about 200 objects per year, the initial design incorporated two 40-cm-diameter, F/1.0 telescopes using 500 by 500 CCD pixel arrays and separated by 1 meter to obtain usable parallax data. However, without on-board data processing, data transmission for this design was much too high. Consequently, fewer and larger pixels were required; however, this significantly increased the separation distance required for the two sensors to make parallax measurements. By optimizing the size, position and readout rate of the pixels, Quicksat was redesigned into two 25-cm-diameter, F/1.0 optics with 9 by 16 pixel arrays, decreasing the spacecraft mass by 200 kg and increasing the expected detection rate by a factor of 10. However, the cost of building and integrating the Quicksat satellite was estimated at more than $100 million; by 1988, the free rocket was unavailable and the project was canceled.
(Utkin et al., 1993); German experts, who proposed flying optical sensors on a space station or the U.S. Space Shuttle (Bendisch et al., 1993); and U.S. experts. In the United States, NASA (working with Ball Corporation) has done extensive work on an infrared system for debris detection and collision warning for the Space Station and has proposed a spacecraft (see Box 2-5) with two small telescopes capable of monitoring the 1-mm and larger environment (Portree and Loftus, 1993). In addition, Kaman Sciences Corporation has proposed an optical (visible and infrared) debris detection and characterization system for use on the U.S. Space Shuttle, and the U.S. Department of Energy's National Laboratories (specifically Sandia, Los Alamos, and Livermore), along with several companies, have each proposed various sensors (including radar, infrared, optical, and LIDAR) as potential space-based debris detection sensors. In early 1995, the U.S. Department of Defense plans to launch its MSX (Midcourse Space Experiment) spacecraft, which will use ultraviolet, infrared, and visible light sensors developed for other purposes to search for uncataloged debris.
Both passive or active remote sensors in orbit could theoretically be used to detect debris. Passive sensors (such as telescopes) detect objects by using existing illumination (such as reflected sunlight or the infrared radiation emitted by heated objects). Active sensors (such as LIDAR or radar) illuminate an object and detect the reflected illumination. One advantage of active sensors is that a single active sensor can accurately