USAF PERSPECTIVES ON LEONID THREAT AND DATA GATHERING CAMPAIGNS MARVIN H. TREU Space Reconnaissance Requirements Division, HQ USAF/XORR, Pentagon, Washington DC E-mail:
[email protected]
SIMON P. WORDEN Deputy Director of Command and Control, HQ USAF/XOC, Pentagon, Washington DC
MICHAEL G. BEDARD Commander, 46 Weather Squadron, Eglin AFB, FL
and RANDALL K. BARTLETT Program Office, Assistant Secretary of the Air Force (Space), Washington DC
(Received 10 July 2000; Accepted 7 September 2000)
Abstract. The Air Force has long recognized the threat posed by the space environment to military satellite systems including the potential for disastrous effects resulting from a meteoroid impact. This concern has steadily elevated with our nation's increasing reliance on space assets for systems critical to national defense. The 1998/1999 Leonid Meteor Storm Operational Monitoring Program was initiated to address this threat. The goal of this Air Force-led, international cooperative program was to provide near real-time Leonid meteor flux measurements to satellite operators. The incorporation of these measurements with model predictions provided an approximate 2-hour lead warning of the peak storm activity, permitting satellite operators ample opportunity to exercise hazard mitigation procedures. As a result, Department of Defense (DoD) and other participating satellite operators may have helped avoid spacecraft damage. The extent of any minor damage to components impossible to detect by operators is difficult to ascertain and may not manifest itself for a period of time. Modest micrometeoroid precipitation may reduce spacecraft life expectancies as a consequence of the physical erosion or sandblasting of exterior surfaces, and damage sustained by electronic systems from concurrent high-energy plasma discharges. Later effects could take the form of premature failure of satellite sensors and other spacecraft components, leading to overall shortening of satellite mission duration. The Air Force intends to pursue further analysis of data and polling of satellite operators to fully assess the Leonid '99 event. Future U.S. Air Force involvement may include support for additional observations and analysis. Earth, Moon and Planets 82–83: 27–38, 2000. c
2000 Kluwer Academic Publishers. Printed in the Netherlands.
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Keywords: meteor storm, satellite impact hazard, space weather, Leonids 1999, situation awareness.
1. Introduction In response to the potentially disastrous threat posed by meteors to DoD satellite systems, the U.S. Air Force teamed with government, commercial and academic research institutions to initiate the Leonid Meteor Storm Operational Monitoring Program. Beginning as a lowlevel effort in 1997, it evolved into a full-scale, worldwide scientific expedition in 1998 and 1999. With space systems becoming increasingly important to U.S. national security, threats posed to our satellite constellation must be monitored and better understood. This program enabled satellite operators to monitor the storm in near realtime, providing them with an opportunity to mitigate the threat by exercising risk-reduction actions. The quality and quantity of data collected during the 1999 storm is unprecedented. Analysis of this data will provide a better understanding of meteors, improved prediction modeling of future events and determine the best strategy for future meteor storm encounters. Although the Air Force does not plan to support a large-scale deployment to observe the Leonid meteor shower in the near future, support may be provided for additional data analysis and limited additional observations.
2. Meteors - space environment threat to DoD systems Both the U.S. military and intelligence community are becoming increasingly reliant on space systems to achieve mission success. This was shown most dramatically in the last decade during conflicts beginning with DESERT STORM and concluding with operation ALLIED FORCE. The 1999 National Security Strategy recognizes the importance of space by stating: “unimpeded access to and use of space is a vital national interest -- essential for protecting U.S. national security, promoting our prosperity, and ensuring our well-being.” Space systems today enable our military leaders to dominate the battlefield by providing global communications, precise navigation, accurate meteorological data, early warning of missile launches, and near real-time signals and
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imagery intelligence support (Hall, 1998). Figure 1 depicts the historical use of space assets from the early 60’s to the present. Space – communication, weather, intelligence, navigation, and early warning – greatly enhanced military operations in time to support the war in Iraq in the early 90’s. Today’s senior leaders recognize that controlling space will be a foremost objective in future military contingencies. Air Force Chief of Staff, General Michael E. Ryan recently stated, "We couldn't do the operations we're doing without space." (AF Policy Ltr, 1999).
Figure 1. Integration of space with warfighting capabilities. The trend of leveraging space for warfighting so powerfully demonstrated in DESERT STORM in the early 90’s continued through the end of the century. Flexible targeting, reachback, bomb and missile impact reporting, and GPS-guided munitions are examples of how space assets were used in operation ALLIEDFORCE. Flexible targeting, the capability to redirect airborne assets to higher priority targets while in flight, is possible due to information from space-based assets being provided directly into the cockpit. Higher bandwidth and leveraging commercial satellite communication allowed unprecedented “reachback” capability for American troops. Leaving more personnel at their home bases to remotely provide information and tools needed for the combat troops is only possible through the exploitation of space. Reducing the
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in-theater personnel footprint is cheaper, safer, and a simpler means to conduct war. New data processing capabilities of the Defense Support Program (DSP) provided space operators with a tool to report near realtime bomb and cruise missile impacts. This allows planners to assess attack effectiveness and build future strike packages. Finally, perhaps the most dramatic example of leveraging space in "Allied Force" was the increasing use of Global Positioning System (GPS)-guided munitions. The Joint Direct Attack Munition (JDAM) provided a remarkably accurate tool for bombing a target - even in adverse weather conditions (cloud obscuration of targets) (Eberhart, 2000). In the future, U.S. forces will rely upon space systems for global awareness of threats, swift orchestration of military operations, and precision use of smart weapons (Hall, 1998). The Air Force today is continuing its efforts to evolve toward a full spectrum, Aerospace Force, indicating the importance of not only using space as a medium to support military forces, but a medium through which to employ and maintain power. With this increasing reliance on space systems for successful accomplishment of military missions, threats to DoD and other spacecraft utilized for defense purposes must be taken seriously. One example of a natural threat is from potential meteoroid impacts on spacecraft. Unfortunately, meteor storms are one of the most poorly understood phenomena in our Solar System (Beech et al., 1995). The damage potential ranges from surface sandblasting and possible mechanical damage to complete loss of the spacecraft. The most probable risk, however is the result of impact-induced electrostatic discharge. This occurs when a meteoroid impacts the satellite surface, generating a charged plasma capable of producing a current “spike.” The damage caused by this discharge can sometimes prove to be fatal to a satellite. This type of event is believed to have caused the end-of-life anomaly on Olympus, the European Space Agency’s experimental communications satellite on the night of 11-12 August 1993 (Caswell et al., 1998). On this night of the predicted peak of the Perseid meteor shower, Olympus lost its earth pointing ability and entered into a spin. Efforts to recover control of the spacecraft depleted its fuel. With insufficient propellant available to recover and continue operations, the spacecraft was removed from its orbit - ending the mission. Although a Perseid impact cannot be conclusively shown, one of several meteor effects (structural damage, momentum transfer, creation of a plasma cloud, and the triggering of discharges of previously charged surfaces) is
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the most probable explanation for the demise of Olympus (Caswell et al., 1998).
Figure2. Penetrating fluence of the natural meteoroid complex and a Leonid storm with peak ZHR of 15,000. Reprinted from: Planetary Space Science, Vol. 47, 1999, McBride et al., "Meteoroid impact on spacecraft: sporadics,...", p. 1011, (c) 1999, with permission from Elsevier Science.
The Leonid meteor shower is of particular concern to the DoD due to the potential for considerable risk to the satellite population during ‘storm’ conditions (Beech and Brown, 1993). The cause of the concern stems from hypervelocity impact and the anticipated flux. The relative geocentric encounter velocity of a Leonid at the top of the atmosphere is ~71 km/s (McBride and McDonnell, 1999). With meteor penetration potential varying with the square of the velocity (V2) and current production proportional to V4, a Leonid meteor impact clearly poses a high threat to spacecraft. The threat from a low number of high velocity meteors would not warrant significant concern to satellite operators. The flux from the Leonid shower however easily distinguishes this threat from other meteor or sporadic events. The instantaneous storm flux required to penetrate a surface can exceed the background by several orders of magnitude (Figure 2). A good way to translate the pertinent variables of velocity, size distribution and flux threat to officials in the Air Force and U.S. Government is to describe the exposure risk to the satellites. The penetrating fluence encountered during a two-hour peak
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of a Leonid storm is equivalent to a year of exposure risk from background meteors.
3. Leonid storm operational monitoring program In response to the increasing reliance of the DoD (as well as civil and commercial organizations) on space combined with limited understanding and data available on meteor storm threat to spacecraft, the Leonid Meteor Storm Operational Monitoring Program was developed. The dual purpose of this Air Force/NASA co-sponsored program was to: (1) provide near real-time Leonid meteor flux measurements to satellite operators, and (2) use the data to better understand and model these events. While the Air Force interest is more operationally focused toward satellite impact hazard, NASA has additional scientific interests relevant to astrobiology and the origin of the solar system. The data gathering campaign was subsequently designed to provide near real-time data to satellite operators and collect data for research purposes. Ground-based radar and electro-optical instrumentation were deployed to support the near real-time flux measurements, while two USAF aircraft collected both real-time data and scientific mission data. Collecting data was the first step in the program. Processing the data into a useful form and disseminating it to the satellite operators requires as much consideration and planning. The users themselves were responsible for accomplishing the final step - how to use the data to protect the spacecraft. There are a number of options available to protect or mitigate the effects of meteor impacts on a spacecraft. The most effective is spacecraft and sensor hardening, however this can be a costly solution and is obviously not a possible option for satellites already in orbit. Other mitigation procedures were employed by the Air Force and documented in operations plans (OPlans). First, the meteor flux data provided satellite operators with situational awareness. Just knowing the threat and being alert to the possibility of meteor impact or effects proved invaluable to operators. If an anomaly were to occur during peak meteor activity, critical time could be saved in determining the specific cause and most appropriate corrective action. Proactive measures include turning off critical or sensitive sensors and avoiding command and control contacts during the peak of the storm event. Doing this reduces the opportunity for bit-flips, single-event upsets, or other disruption in a
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command sequence to place the satellite at increased risk of mission downtime. Reorientation of larger spacecraft is an option considered to minimize the surface profile exposed to the meteor stream. Some systems propose orienting their solar panels parallel to the stream to reduce the probability of impact. A final action pursued in the Oplans is to either bring in or place “on-call” the most experienced satellite operators during the storm peak. The most experienced personnel are best qualified to quickly diagnose and react to anomalous satellite behavior induced by meteor impact and associated effects.
Figure3: Map showing the location of the LEOC (Leonid Environment Operations Control center) at NASA Marshall Space Flight Center in Huntsville, AB, the six electro-optical (EO) sites around the world, and the location of the dual-frequency radar in Alert, Canada. From: Brown, et al. (2000).
4. Campaign summary The Leonid Meteor Storm Operational Monitoring Program consisted of three important components: the ground-based campaign, the airborne campaign, and the data processing and dissemination segment. Dr. Peter Brown of the University of Western Ontario developed the Concept of Operations (CONOPS) and led the ground-based observation
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and data collection campaign. The CONOPS was perfected over the past three years and worked extremely well in 1999 despite additional observing locations and the challenge of adverse weather at multiple sites. Both electro-optical (low-light television) and radar equipment were used to collect data (Brown et al., 2000). Human observer and Science Applications International Corporation (SAIC) real-time detection algorithms were used to provide meteor counts. The image intensified charge-coupled device (CCD) detectors were deployed to the Negev Desert, Israel (primary site); Las Palmas, Canary Islands, Spain; Key West, FL; Haleakala, HI; and Kwajalein Atoll, Marshall Islands (Figure 3). The locations were selected based on climatology (to offer the best chance for cloud-free, unobstructed observing), and maximum viewing time of the event – 22 hours. For full 24-hour, all-weather coverage, a mobile, multi-high frequency (HF) radar was placed at Alert, Nunavut, Canada. These ground sensors provided proven, extensive coverage for the storm, while NASA airborne sensors offered a means to mitigate the risk of weather obstruction in addition to providing complementary science collection value. Dr. Peter Jenniskens and Capt Steve Butow, both with the Search for Extraterrestrial Intelligence (SETI) Institute, led the 1999 NASA Leonid Multi-Instrument Aircraft Campaign (Leonid MAC), with a prior mission in 1998. Their 35+ member airborne team performed high altitude stereoscopic observations of the Leonid meteor components using low light level video, UV/visible spectrometers, High Definition Television (HDTV) imagers, and near and mid-infrared spectrometers and scanning imagers (Jenniskens et al., 2000). The purpose was to determine meteor flux, orbital elements, composition, structure, ablation properties and disposition of meteoric debris for studies related to the origins of life and space weather hazards. HQ USAF/XO co-sponsored the airborne campaign specifically to collect flux data from above obscuring clouds. The high altitude also provided the most precise counts, showing the early rise of the storm profile. The Leonid MAC flux data were transmitted in near real-time to the operations center through space-based telemetry systems including INMARSAT and the Multi-Source Tactical System (MSTS) TRACK II. The MSTS TRACK II provides en route aircraft tracking as well as burst transmission of email via secure UHF SATCOM between aircraft and ground-based mission command and control at NASA Ames Research Center (ARC) in California.
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Dr. Bill Cooke (Computer Sciences Corporation, Marshall Space Flight Center/Space Environment Group) and Dr. Rob Suggs (Marshall Space Flight Center/Space Environment Group) established and led the Leonid Environment Operations Center (LEOC). The LEOC collected the observed data from the worldwide network of ground optical and radar observers and the Leonid MAC airborne observers, performed realtime data analysis and transmitted the results to satellite operators via email. This information was also posted on a secure internet site (Figure 4). Approximately 100 authorized web users and 200 e-mail customers received the LEOC data. The incorporation of these measurements with model predictions provided ample lead warning during the onset of the storm peak. The Marshall team developed the CONOPS for the data assimilation and analysis task responsible for the Leonid flux data getting to the user in near real-time. Providing the resources for a program of this magnitude proved challenging. To accomplish all the goals of the mission, over 25 international government, educational and private organizations cooperated by providing funding, personnel, or other in-kind support. The ground-based (including the LEOC at MSFC) and airborne campaigns cost nearly $2M (US). This purchased near real-time reporting, deployment (equipment, personnel, and USAF aircraft), analysis, optimal equipment re-configuration, modeling and management infrastructure. The USAF provided 45% of the funding required to support the operational aspect of the campaign. NASA (HQ, MSFC, and ARC) provided 49% of the funds supporting both the airborne effort as well as operation of the LEOC. Required personnel came from USAF, NASA, government contractors, university researchers and even student volunteers. The in-kind support from Canadian Forces and Israel was essential to the mission. The Leonid Meteor Storm Operational Monitoring Program was a success. The 1999 Leonid meteor shower reached modest storm strength (ZHR ~3,700) and lasted approximately 90 minutes. Predictions of the peak were remarkably accurate. McNaught and Asher (1999) predicted the actual peak time of 02:08 ± 15 min. UTC (Universal Time, Coordinated) on November 17, while Brown's (1999) forecast was nearly as accurate at 02:20 UTC. All customers received the data they required in a timely fashion and reported no satellite impacts or anomalies. An intensive post-event data reduction effort is underway on a very unique data set. The data collected during the 1999 Leonid meteor storm marks the first time in history radar and electro-optical
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real-time meteor observations were combined in a global manner to produce a snapshot of the meteoroid environment in near-earth space. In addition, this is one of the largest data sets ever collected on a meteor shower from a single campaign. More data now exists from the 1999 Leonids than from all the data from all previous data collection efforts. Lessons learned in the aftermath of the program identified a few areas for improvement. The amount of coordination between the airborne and ground components of the campaign prior to the shower was underestimated. Telemetry testing between the LEOC at NASA MSFC and NASA Ames required advance testing but was not possible due to aircraft and avionics availability. More time and work was also required to determine the proper means of synthesizing video, radar, and visual near real-time meteor observations. A software problem when the ZHR exceeded 150 and a power failure on one of the radar frequencies were unanticipated events that prevented the reporting of absolute flux values. This resulted in an underestimated flux by a factor of 2-3. Finally, it was determined that while automated detection instrumentation is useful, the most reliable and best sensor is the trained meteor observer.
Figure 4. Near real-time data output from the Leonid Environment Operations Center.
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5. Future plans The Air Force is not planning to participate in a Leonid shower operational monitoring and data gathering campaign in November 2000. Because of the low peak rates expected, resources will be better spent investigating the spatial density and other characteristics of the 1866 Leonid stream. This stream is projected to be the primary contributor to the Leonid event in 2000. This work will also help refine the Leonid meteor forecast development for years 2001-2002. The science campaign should de-emphasize ground video and visual observations in 2000 because of moon phase (last quarter, high in the sky and close to the radiant of the shower).
6. Conclusions The 1999 Leonid Operational Monitoring Program was a complete success. A consortium of over 25 multi-national government organizations teamed with academia and industry to deploy scientists, researchers, and volunteers around the world. This team observed from the ground and in the air the largest meteor storm in nearly 35 years. The data collected was quickly analyzed and distributed to satellite operators for their situational awareness and protection of critical spacecraft. In addition to developing preventative measures to minimize the risk to satellites for this storm, tremendous benefit was gained by documenting procedures and OPlans to address a naturally occurring threat in space. The experienced gained from this campaign will prove to be useful in the future. A secondary goal of the program was to assemble a comprehensive data set from ground and airborne observations to improve our understanding and modeling of future meteor events. The unique, most comprehensive data set collected to date is anticipated to meet the expectations of researchers. Before anticipating a follow-on meteor observing campaign of this magnitude, the Leonid’s 1999 data set must be completely reduced. The focus must now be on reducing this existing data, not planning the next operational program. If more data is required to better understand the threat of these meteor events to the operation of artificial satellites, a clear and convincing argument must be provided to
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support the remaining gap in understanding. Until this time, the successful partnerships forged in this campaign must continue. Future Air Force participation could include possible low-level support for data reduction, including some potential low-level observing support from a proper USAF source, such as the Air Force Research Laboratory.
Acknowledgements Editorial handling: Mark Fonda.
References Beech, M. and Brown, P.: 1993, MNRAS 262, L35–L36. Beech, M., Brown, P., and Jones, J.: 1995. Q. J. R. astr. Soc. 36, 127–152. Brown, P.: 1999, Ph.D. Thesis University of Western Ontario, University of Western Ontario, Canada. Brown, P., Campbell, M.D., Ellis, K.J., Hawkes, R.L., Jones, J., Gural, P., Babcock, D., Barnbaum, C., Bartlett, R.K., Bedard, M., Bedient, J., Beech, M., Brosch, N., Clifton, S., Connors, M., Cooke, B., Goetz, P., Gaines, J.K., Gramer, L., Gray, J., Hildebrand, A.R., Jewell, D., Jones, A., Leake, M., LeBlanc, A.G., Looper, J.K., McIntosh, B.A., Montague, T., Morrwo, M.J., Murray, I.S., Nikolova, S., Robichaud, J., Spondor, R., Talarico, J., Theijsmeijer, C., Tilton, B., Treu, M., Vachon, C., Webster, A.R., Weryk, R. and Worden S.P.: 2000, Earth, Moon and Planets 82–83, 167–190. Caswell, R. D., McBride, N., and Taylor, A.: 1998, in Lynch et al. (eds)., Leonid Meteoroid Storm and Satellite Threat Conference Proceedings (no pagenumbers). Eberhart, R. E.: 2000, Statement by Commander-In-Chief, North American Aerospace Defense Command and United States Space Command Before the United States Senate Armed Services Committee, Strategic Subcommittee 8 March 2000. Hall, K. R.: 1998, Statement by Assistant Secretary of the Air Force (Space) and Director, National Reconnaissance Office, Keith R. Hall, on U.S. Spacepower in the 21st Century 29 September 1998. Jenniskens, P., Butow, S.J., and Fonda, M.: (2000) Earth, Moon, and Planets 82–83, 1–26. McBride, N. and McDonnell, J.A.M.: 1998, Planet. Space Sci 47, 1005–1013. McNaught, R.H. and Asher, D.J.: 1999, WGN, Journal of the IMO 27, 85–102.
