A publication of The Orbital Debris Program Office NASA Johnson Space Center Houston, Texas 77058 October 1998 Volume 3, Issue 4. NEWS Imagery Survey of the Hubble Space Telescope During the second servicing mission of the measurements of the impact features. expected exponential increase down to a size Hubble Space Telescope (HST) by the STS-82 of 0.4-0.5 cm, where sensitivity limits of the mission in February 1997, an extensive Over 500 of the impacts were found on the aft imagery apparently lead to a reduced count. imagery survey was performed covering shroud and equipment section where highly The distribution of impacts around the aft approximately 97% of the HST surface. The reflective surfaces facilitated detection of shroud suggest a real difference in the number results of a dedicated study to of particle impacts on the +V3 and identify and to characterize the –V3 sides. apparent micrometoeoroid and orbital debris (M/OD) impacts An attempt was also made to have been recently documented compare the number of impacts in a new NASA JSC report, seen on the first servicing mission "Survey of the Hubble Space in December 1993 (after 44 months Telescope Micrometeoroid and exposure in LEO) and the second Orbital Debris Impacts from servicing mission (after an Service Mission 2 Imagery," by additional 38 months exposure in G. J. Byrne, D. R. Bretz, M. H. LEO). A limited comparison of the Holly, M. T. Gaunce, and C.A. +V3 quadrant showed an increase in Sapp. the density of observed strikes from approximately 5 impacts per square Employing video, photography, meter to approximately 20 impacts and electronic still imagery (a per square meter. While some of total of 2500 still frames and 17 this increase is undoubtedly due to hours of video), the analysis Figure 1. Hubble Space Telescope, Major Components, the superior quality of the imagery team was able to identify 788 and Coordinate Systems obtained during the second potential impacts on the HST aft servicing mission, a change in the shroud, equipment section, aft bulkhead, impact features. Approximately 80% of the environment may also be indicated. grapple fixtures, aperture door, and solar impact zones measured less than 0.8 cm, arrays. The analysis process involved first although the largest was 4.7 cm in diameter. The next servicing mission to HST is screening and categorizing the images, then scheduled for May 2000, and an additional imagery review and M/OD impact A plot of the number of impacts of a given imagery survey is planned. identification, followed by mapping and outer diameter size range illustrates the (Figures continued on page 2) Inside... Solitary Breakup and Anomalous Events in Third Quarter are Familiar .............................................3 New Report on Historical Satellite Fragmentations ................................................................................4 Post-flight Examination of the STS-87 Orbiter ......................................................................................5 Breakup Model Update: Part II, Delta Velocity Distribution ................................................................6 JSC IAF Abstracts ............................................................................................................................. 7 1 The Orbital Debris Quarterly News Project Reviews, Continued Imagery Survey of the Hubble Space Telescope, Continued (Continued from page 1) Figure 2. EVA Camera Image of MMOD Strike on -V2 Aft Shroud Door Figure 3. Size Distribution of Impact Primary Outer Diameters 2 The Orbital Debris Quarterly News NEWS, Continued Solitary Breakup and Anomalous Events in Third Quarter are Familiar During July and August Naval Space posigrade and retrograde pieces could easily be fragments on two different occasions in 1995. Operations Center personnel identified one hours apart. Within a week preliminary The orbit at the time of the event was satellite breakup and found evidence of three element sets had been generated on 40 objects, approximately 535 km by 650 km with an anomalous events. The breakup was but none had been officially cataloged. inclination of 100 degrees. Since 1985 at least discovered on 3 August when more than 110 three other debris from the original breakup debris from a Proton fourth stage ullage motor This ullage motor had been in orbit for 9 years have also fragmented with multiple new debris (Russian designation SOZ) penetrated the and 7 months before the event, a record period being produced each time. Navy’s electronic fence which spans the of dormancy for this object class. In fact, the southern United States. Launched in last four such breakups (one in 1996, one in On 1 August the PARCS radar in North Dakota conjunction with a GLONASS high altitude 1997, and two in 1998) had been in orbit longer detected a new piece of debris which mission on 10 January 1989, the unit (Satellite than any of their fragmenting predecessors with apparently originated from the old U.S. Number 19755, International Designator 1989- an average age of 9.0 years compared to the 3.6 SEASAT spacecraft (Satellite Number 10967, 001G) was in an orbit of 340 km by 19,055 km year average for the earlier 13 breakups. No International Designator 1978-064A). Since with an inclination of 64.9 degrees at the time Proton ullage motor breakups have yet been 1983 SEASAT, which is currently in a nearly of the event. This was the 17th known breakup identified with missions flown after 1994. A circular 765 km orbit with an inclination of 108 of a Proton SOZ ullage motor since the first total of 73 intact ullage motors (60 from 1994 degrees, had previously spawned eight one exploded in 1984. or earlier) were still in orbit during July. In cataloged debris on various occasions with only addition, despite the fact that two ullage motors three still remaining in orbit. Debris detections began late on 3 August and are released on each mission, no two of the 17 continued steadily for over two hours. The breakups to date have involved motors from the Finally, a 17-year-old Soviet rocket body figure below identifies 81 objects believed same flight, possibly suggesting a difference in (Satellite Number 12519, International associated with this event. The change in design or operation. Designator 1981-054E) may have shed a piece longitude simply corresponds to the rotation of of debris in late July. The Molniya upper stage the Earth as the debris plane passes through the Three anomalous events associated with old was in a highly elliptical orbit with a perigee wide sensor fence. The quick spread of the resident space objects were also noted during below 100 km and an inclination of 62 degrees. debris along the orbit plane was made possible the quarter. A fragment (Satellite Number The very low perigee suggests that the piece by the large semi-major axis. Orbital period 4869, International Designator 1970-025EZ) separation may have been induced by differences of as much as 45 minutes were associated with the 1970 Nimbus 4 upper stage aerodynamic stresses. An element set was possible with less than 200 m/s ejection breakup apparently broke into two pieces on 2 created on the new piece, but the object may velocity. Thus, after a very short time July. This object had previously shed have decayed rapidly. Detections of debris from Satellite No. 19755 by Naval radar surveillance system, 3 August 1998. 3 The Orbital Debris Quarterly News News, Continued New Report on Historical Satellite Fragmentations The 11th edition of the History of On-Orbit contains information on 152 known breakups new edition which is now available to the Satellite Fragmentations (JSC-28383) was and 33 anomalous events. Debris from these orbital debris community. released in August. The cut-off date for events 152 events accounts for 41% of the total was June 30, 1998. This is the 1st edition cataloged on-orbit Earth satellite population of The current authors would also like to thank the compiled and published by the Orbital Debris 8575 objects. Just 10 of more than 3900 Space authors of the previous editions of this Program Office at the NASA JSC, with support missions flown since 1957 are responsible for document for making their input data available. from Lockheed Martin Space Mission Systems 25% of all cataloged artificial Earth satellites In addition, the assistance of personnel of U.S. and Services. Previous editions were prepared presently in orbit (Figure 1). Moreover, the Space Command, Air Force Space Command, by Teledyne Brown Engineering (TBE), under sources of 9 of these 10 fragmentations were Naval Space Command, and Teledyne Brown the sponsorship of the NASA JSC. discarded rocket bodies which had operated as Engineering has been vital to the present work. designed but later broke-up. Rocket bodies are This document, often used by orbital debris the primary sources for debris in orbit today. modelers as a database and reference, now This and other information can be found in the 400 355 350 300 275 273 250 212 200 200 190 178 153 150 142 129 100 Number of remaining In-Orbit Debris 50 0 1994-029B 1981-053A 1970-025C 1992-093B 1961-015C 1975-052B 1973-086B 1976-077B 1978-026C 1974-089D Mission International Designator Figure 1. Magnitude of the ten largest debris clouds in orbit as of June 30, 1998. The Reentry of Potential Risk Objects In 1997 the Inter-Agency Space Debris 1991, but the possibility of debris surviving The largest object currently in Earth orbit is the Coordination Committee (IADC) adopted an reentry warrants special international attention. Mir space station with a mass of more than 120 action item to establish an informational metric tons without crew and cargo resupply network for the timely exchange of data on the In September 1998 the main node for this new vehicles. Russian officials have announced orbital parameters and impact predictions for communications network, located at ESA's their intention to deorbit Mir in a controlled space objects assessed to pose potential risks to European Space Operations Center, was tested manner on 8 June 1999.