dium-sized debris objects. Figure 3-8 shows the estimated population distribution of objects detected by the Haystack radar when parked vertically, as compared with the population distribution of objects in the U.S. catalog. Interestingly, the data show that for the region measured, the altitude distribution of medium-sized objects is similar to that of the larger objects included in the U.S. catalog. There are, however, two significant differences: (1) below about 1,000 km the population of medium-sized objects detected by Haystack declines with decreasing altitude faster than the population of large cataloged objects; and (2) around 900 to 1,000 km there is a large peak in the population of medium-sized objects detected by Haystack with no corresponding peak in the population of large cataloged objects. The first difference is consistent with the expectation that medium-sized pieces of debris are more strongly affected by atmospheric drag than larger debris. The peak in the medium-sized population around 900 to 1,000 km, however, points to a source of debris other than previously recorded breakups.

The eccentricity and inclination of many of the medium-sized objects detected by Haystack can also be determined. The data on inclination versus altitude for the objects detected by the Haystack radar are depicted in Figure 3-9. These measurements show that medium-sized de-

FIGURE 3-8 Estimate of LEO mid-sized orbital debris population from Haystack radar sampling (90 degrees, 547.6 hours), compared to the U.S. Space Command population of cataloged objects.

SOURCE: National Aeronautics and Space Administration.



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