A publication of The Orbital Debris Program Office NASA Johnson Space Center Houston, Texas 77058 July 2002 Volume 7, Issue 3. NEWS A New Collision in Space? A 30-year-old spacecraft was apparently 539 (1972-102A, U.S. Satellite Number 6319) radiation environment of outer space and to struck in April by a small piece of orbital debris and calculated that the fragment was ejected sub-millimeter particle impacts. or a meteoroid. The event, which occurred at from the spacecraft on 21 April at a relative Also immediately obvious was the high an altitude of approximately 1370 km, was velocity of 19 m/s. The newly created debris susceptibility of the fragment to solar radiation sufficient to alter the orbit of the spacecraft and was cataloged as U.S. Satellite Number 27423 pressure, demonstrated by rapid and dramatic to produce a new piece of debris which was on 6 May. changes in its orbit. From an initial orbit of large enough to be tracked by several sensors in The magnitude of the ejection velocity was about 1365 km by 1445 km with an inclination the U.S. Space Surveillance Network (SSN). far greater than is customary for what are of 74 degrees, the fragment’s perigee began to Radar returns suggest the fragment diameter known as anomalous events, i.e., infrequent decrease while its apogee increased. Within was between 20 and 50 centimeters. piece separations from older spacecraft and four weeks the orbit had been perturbed into Analysts of Air Force Space Command’s upper stages of launch vehicles. The causes of one of 750 km by 1895 km. At this point, 1st Space Control Squadron in Cheyenne these debris-producing events are thought to be atmospheric drag became the dominant factor, Mountain near Colorado Springs, Colorado, related to the degradation of satellite surface causing the object to reenter the atmosphere a noticed a new object in the vicinity of Cosmos materials under the harsh temperature and little more than two weeks later on 3 June (see figure). Thus, the fragment existed for only 43 2000 days, despite originating in an orbit from which decay normally requires thousands of years. Of equal interest was the behavior of the 1600 parent satellite, Cosmos 539. At the time of the event the spacecraft was in an orbit of approximately 1340 km by 1380 km. Satellite 1200 tracking data indicated that a small but permanent change in the orbit of Cosmos 539 coincided with the creation of the piece of Altitude (km) Altitude 800 debris. Such an orbital perturbation would be a natural result of a collision with a small object. The orbital period of the spacecraft was Apogee 400 reduced by nearly a second. Taking into Perigee account the mass of the spacecraft, this change in orbit could have been caused by a collision 0 with a meteoroid or orbital debris only a few 2002.3 2002.32 2002.34 2002.36 2002.38 2002.4 2002.42 centimeters in diameter. Orbital debris are Epoch typically more dense than meteoroids, but their collision velocities are lower. The probability Orbital history of the fragment released from Cosmos 539 (April-June 2002). (Continued on page 2) Inside... Tools for Rule-of-Thumb Calculations for Orbital Debris .....................................................2 Optical Observations of GEO Debris ....................................................................................... 4 Satellite Breakups Remain a Problem After 40 Years .............................................................5 1 The Orbital Debris Quarterly News NEWS A New Collision in Space?, Continued (Continued from page 1) August 1997, more than seven years after being higher orbit. of collision with any object of this size, which is decommissioned, the NOAA 7 spacecraft Although it remains possible that on-board below the detection threshold of the SSN, is (1981-059A, U.S. Satellite Number 12553) also energy releases from the two long-dead low; however, at this altitude the flux of demonstrated an abrupt 1 second change in its spacecraft could have caused these events, the centimeter-size orbital debris is approximately orbital period, accompanied by the release of circumstantial evidence points toward collisions 10 times that of meteoroids. three debris. Although two of the new debris with unseen objects. This event is reminiscent of an anomaly were released with low relative velocities, one experienced by the NOAA 7 spacecraft. In of the fragments was thrown into a noticeably Publication of the FY99 CDT Report K. S. Jarvis Geosynchronous Earth Orbit (GEO). The CDT operation are computer controlled to automati- The report (JSC-29712) “CCD Debris is equipped with a SITe 512 X 512 CCD cally collect data for an entire night. The CDT Telescope Observations of the Geosynchronous camera. The pixels are 24 microns square (12.5 has collected more than 1500 hrs of data since Orbital Debris Environment, Observing Year arcseconds) resulting in a 1.7 by 1.7 degree November 1997. This report describes the 1999” has been published. NASA has been field-of-view. The CDT system is capable of collection and analysis of 81 nights (~530 using the Charged Coupled Device (CCD) detecting 17th magnitude objects in a 20 second hours) of data collected in 1999. It is available Debris Telescope (CDT), a transportable 32-cm integration which corresponds to a ~0.6-meter upon request. Schmidt telescope located near Cloudcroft, NM, diameter, 0.20 albedo object at 36,000 km to help characterize the debris environment in altitude. The telescope pointing and CCD Second Identified Satellite Breakup of 2002 The second satellite breakup of 2002 has Ariane geosynchronous transfer missions in vehicle. been belatedly identified. Tracking data from September 1993. No Ariane launch vehicle A two-year-old Chinese Long March 4B the U.S. Space Surveillance Network now launched since that time is known to have upper stage (2000-050B, U.S. Satellite Number indicates that an Ariane 4 upper stage (1992- experienced an on-orbit fragmentation. 26482) was the source of at least two new 041C, U.S. Satellite Number 22032) generated During the second quarter of 2002, three debris in mid June. The event occurred after at least nine pieces of debris in February. At minor debris-producing occurrences also took the stage had fallen to 30 km below the the time of the event the upper stage was in an place. In May, SSN analysts detected an International Space Station. This was only the orbit of approximately 250 km by 26,550 km anomalous event involving a 16-year-old Soviet fifth Long March 4B upper stage to be placed in with an inclination of 7.0 degrees. Due to low rocket body. The Vostok (also known as SL-3) low Earth orbit, and two of the previous four perigees, all debris are in steadily decaying upper stage (1985-090B, U.S. Satellite Number stages have suffered severe breakups after being orbits and will not present a long-term hazard to 16111) was in an orbit of 510 km by 565 km abandoned, producing hundreds of new debris other resident space objects. with an inclination of 97.7 degrees when a piece large enough to be tracked. This marks the sixth known fragmentation separated on 5 May. Through June the decay Finally, yet another anomalous event of an Ariane 4 third stage. Interestingly, the last rate of the new debris was lower than that of the occurred during the second quarter of 2002, this three vehicles involved in such events (1988- rocket body, which is atypical for debris of this time involving a 30-year-old spacecraft. See 109C, 1991-075C, and 1992-041C) had been in type. Six other Vostok upper stages, aged 8-26 “A New Collision in Space?” in this issue for a orbit 9-10 years at the time of their respective years, have been associated with similar complete description of this unusual breakups. All flights were conducted prior to anomalous events since 1987. These releases of incident. the implementation of passivation measures for debris are probably linked to the design of the Project Reviews Tools for Rule-of-Thumb Calculations for Orbital Debris D. J. Kessler empty envelopes, but I actually used them computer calculations. However, to do this Bob Naumann, who was responsible for frequently for this purpose. Unfortunately, requires insight and some tools. In the past, I some of the best meteoroid measurements and envelopes eventually get lost, along with the have published ways of integrating over various analysis during the 1960’s, once said, “If you documentation of the solutions to those distributions in order to obtain a “properly cannot get an approximate answer to a problems. weighted” average for that distribution. In this problem using the back of an envelope, then I have become a strong believer in the idea article, I will describe one of the tools that I you don't know what you are doing". My desk that one should know the approximate answer have used to understand the relative importance at NASA may have looked like I collected to a problem before tackling it with detailed (Continued on page 3) 2 The Orbital Debris Quarterly News Project Reviews Tools for Rule-of-Thumb Calculations for Orbital Debris, Cont’d (Continued from page 2) approximated by the 1. E+0 8 of various sources of orbital debris. product of the flux at 200 r Meteoroid Flux 1. E+0 7 The cumulative number N of orbital debris µm times the mass of a 200- 1. E+0 6 constant mass or meteoroid particles of mass m or diameter s µm meteoroid. However, 1. E+0 5 1. E+0 4 constant area and greater can be approximated over some this calculation will 1.