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ABSTRACTSAn International Workshop on Collaboration and Coordination Among NEO Observers and Orbital Computers
Kurashiki City Art Museum, Kurashiki, Okayama, Japan
October 23 to 26, 2001
A PROGRESS REPORT ON SPACEWATCHTom Gehrels
University of Arizona
The purpose of the Spacewatch program is to explore the statistics of asteroids and comets as a continuation with CCDs of the photographic Yerkes-McDonald and Palomar-Leiden surveys. The 0.9-meter f/5 Newtonian telescope currently surveys 3000 square degrees per year to a V magnitude limit of 21.7. The 0.9-meter is about to be reconfigured with wider field (f/3) prime-focus optics and an array of four 2048x4608 CCDs. It will continue the limit of V = 21.7 for the surveying, but in stare mode with six times higher rate of sky coverage, probably yielding 300 detections of Earth-approachers, old and new, per year. Astrometry with the 1.8-m telescope began in April of 2001 with a field of view 0.8 degrees (diagonal of the CCD). The 1.8-meter will continue to be dedicated to surveying and follow-up of NEOs that are in urgent need.
SPACEWATCH WEBSITE AND RECENT PUBLICATIONShttp://www.lpl.arizona.edu/spacewatch/index.html
Bottke, W. F., R. Jedicke, A. Morbidelli, J. Petit, and B. Gladman, 2000. "Understanding the Distribution of Near-Earth Asteroids." Science, 288: 2190-2194.
Bottke, W.F., A. Morbidelli, R. Jedicke, J-M. Petit, H. Levison, P. Michel, and T.S. Metcalfe, 2001. "Debiased orbital and size distributions of the near-Earth objects. Icurus, in press.
Durda, D. D., R. Greenberg, and R. Jedicke, 1998. "Collisional Models and Scaling Laws: A New Interpretation of the Shape of the Main-belt Asteroid Size Distribution" Icarus 135: 431-440.
Gehrels, T. 1998. "Detecting Asteroids" Meteorite 2: 18-20 and 3: 18-21.
Gehrels, T. 1999. "A review of comet and asteroid statistics." Earth, Planets, Space 51: 1155-1161
Gehrels, T. 2001 "Collisions with Comets and Asteroids." Sc. American, Decade Choice, in press.
Gehrels, T. 2002. "The Attraction of Asteroids." In Asteroids III, eds. W. Bottke, A. Cellino, P. Paolicchi, and R. P. Binzel, 2002. (Univ. Ariz. Press), in press.
Gehrels, T. and L. Ksanfomality. 2000. "The Search for Earth-Approaching Comets and Asteroids". Solar System Res. 34: 37-48.
Jedicke, R. and T. S. Metcalfe. 1998. "The Orbital and Absolute Magnitude Distributions of Main Belt Asteroids." Icarus 131: 245-260.
Jedicke, R., J. Larsen, and T. Spahr. 2002. "Observational Selection Effects in Asteroid Surveys and Estimates of Asteroid Population Sizes" In Asteroids III, eds. W. Bottke, A. Cellino, P. Paolicchi, and R. P. Binzel (Univ. Ariz. Press), in press.
Larsen, J., A. E. Gleason, N. M. Danzl, A. S. Descour, R. S. McMillan, T. Gehrels, R. Jedicke, J. L. Montani, and J. V. Scotti. 2001. "The Spacewatch Wide Area Survey for Bright Centaurs and Transneptunian Objects." Astron. J. 121, 562-579.
McMillan, R. S. 1999. "The Spacewatch Search for Material Resources Near Earth." Space Manufacturing 12: Challenges and Opportunities in Space: ProC. Fourteenth Space Studies Inst. Princeton Conference on Space Manufacturing, ed. B. Greber (SSI Publ. Princeton, NJ), 72-75.
Ostro, S. J., P. Pravec, L. A. M. Benner, R. S. Hudson, L. Sarounova, M. D. Hicks, D. L. Rabinowitz, J. V. Scotti, D. J. Tholen, M. Wolf, R. F. Jurgens, M. L. Thomas, J. D. Giorgini, P. W. Chodas, D. K. Yeomans, R. Rose, R. Frye, K. D. Rosema, R. Winkler, and M. A. Slade. 1999. "Radar and Optical Observations of Asteroid 1998 KY26." Science 285: 557-559.
Perry, M. L., T. H. Bressi, R. S. McMillan, A. F. Tubbiolo, and L. D. Barr 1998. "The 1.8m Spacewatch Telescope Motion Control System." Proc. SPIE 3351, Telescope Control Systems III, 450-465.
Scotti, J. V. 1998. "Fleeting Expectations: The Tale of an Asteroid." Sky and Tel. 96, 1: 30-34.
THE LOWELL OBSERVATORY NEAR-EARTH-OBJECT SEARCHEdward Bowell
Lowell Observatory, Flagstaff, Arizona, U.S.A.
The Lowell Observatory Near-Earth-Object Search (LONEOS) currently uses a 59-cm Schmidt telescope to discover asteroids and comets that can approach the Earth.
In terms of discovery of larger (> 1 km diameter) NEOs, our search effort has, over the past two years, been the second most effective program worldwide (after LINEAR). As of the end of April 2001, we have discovered 6 Atens, 35 Apollos, 36 Atens, and 13 comets. In three years, we have submitted some 920,000 astrometric observations to the Minor Planet Center. About a year ago, we installed a new Lowell-built camera containing two 2048 x 4096 thinned, back-illuminated chips. Compared to the old camera, the new camera has a shorter read time (12 s vs. 45 s), a higher peak DQE (85%), lower read noise, and far fewer defects. A larger field size (of 8.1 deg2), adoption of new observing techniques, and the application of a better source-detection algorithm have together led to a 7-fold increase in NEO detection rate compared to that at the beginning of 2000.
The LONEOS Schmidt and its operation are now almost fully mature. During the coming year we will implement an image-subtraction method of moving-object detection, which will allow us to work at smaller galactic latitudes; and we will work on exploiting archived images for moving-object data mining. In October 2001, we expect to begin a collaboration with scientists at the U.S. Naval Observatory Flagstaff Station, using a new mosaic camera on their 1.3-m telescope. If we use 45-s integrations, we should cover 60 deg2/hr to V_lim = 21.0 mag. Rough modeling indicates that we should detect between 2 and 3 times more NEAs per unit time compared to the current LONEOS Schmidt's performance. Depending on the time available on the 1.3-m, we should, at the beginning of 2002, double or triple our current discovery rate. In 2005, we expect the Next Generation Lowell Telescope to come online. Planned as a 4-m, f/2.4 reflector having a 3.2 deg2 fov, we should attain hourly coverage of about 50 deg2 to V_lim = 22.3 mag, yielding an NEA detection rate 100 times greater than that of the LONEOS Schmidt.
LINEAR SYSTEMGrant H. Stokes and Jenifer B. Evans
The Lincoln Near Earth Asteroid Research (LINEAR) program has applied electro-optical technology developed for Air Force Space Surveillance applications to the problem of discovering Near Earth Asteroids (NEAs) and comets. LINEAR, which started full operations in March of 1998, has discovered through August of 2001, 682 NEAs, 36 unusual objects, and 65 comets. Over the past 3 years, LINEAR is contributing ~70% of the world-wide NEA discovery rate.
This talk reviews the performance statistics of the LINEAR system addressing the system's sky coverage, detection statistics, and contribution to NASA's congressionally mandated goal of discovering 90% of all large NEAs by 2008.
This work is sponsored by the Dept. of the Air Force and NASA under Air Force Contract No. F19628-00-C-0002. Opinions, interpretations, conclusions and recommendations are those of the authors and are not necessarily endorsed by the United States Air Force.
STATUS OF THE CATALINA SKY SURVEY AND SOUTHERN SURVEYS. Larson, C. Hergenrother, R. Whiteley, T. Kelly, R. Hill, and Rob McNaught*
Lunar and Planetary Laboratory, University of Arizona
*Siding Spring Observatory, Australian National University
The Catalina Sky Survey, down for over a year for upgrades, is now coming back on-line. Upgrades to the Mt. Lemmon 1.5-m telescope are also underway to provide more routine astrometric follow-up and physical observations of the fainter NEOs. During our surveying haitus, we have been obtaining lightcurve and colors of NEOs, and several monolithic very fast rotators have been identified among the smaller NEOs.
The Uppsala Schmidt at Siding Spring Observatory (SSO), Australia is undergoing modifications to provide a similar survey capability at high southern declinations not covered by the northern hemisphere surveys. Critical astrometric observations of PHAs observable from the southern hemisphere are being made with the SSO 1-m telescope.
We will describe the current status of the upgrades and anticipated improvements in coverage and depth of surveying. This work is supported by NASA's Near Earth Object Observation program.
ASTEROID OBSERVATIONS IN BISEI SPACEGUARD CENTERMakoto Yoshikawa and BATTeRS
Bisei Spaceguard Center (BSGC) is a facility to observe near earth asteroids and space debris. It was built by Japan Space Forum (JSF) in 1999, and since the beginning of the year of 2000, observations have been carried out by Japan Spaceguard Association (JSGA) with the financial support from National Space Development Agency of Japan (NASDA). At present (July 2001), two small telescopes (25 cm and 50 cm) are working for test observations. Up to now, we found one Apollo type asteroid (20826) 2000 UV13, which is the second brightest one in the Apollo type asteroids. In addition to this we found more than 100 new asteroids. They are main belt asteroids, because the limiting magnitude of the system in the test phase is about 18.5. However, in the summer of 2001, the 1.0 m telescope will be installed in BSGC. Then we will start full observations.
THE ONDREJOV NEO FOLLOW-UP PROGRAMME: LIGHTCURVE AND ASTROMETRIC OBSERVATIONS OF NEAR-EARTH ASTEROIDPetr Pravec
I will review the NEO Follow-Up Programme conducted at the Ondrejov Observatory of the Astronomical Institute of the Czech Academy of Sciences since 1993. The observations are made with the 0.65-m telescope equipped with inexpensive, small-field CCD cameras, currently a thinned CCD with a FOV of 18'x18' and the limiting effective V magnitude of 20.5 for a 3-min integration time with no filter. The observational program consists of two main parts: (1) lightcurve observations of NEAs in favorable conditions (often shortly ---days and weeks--- after their discoveries); (2) astrometric observations of newly discovered NEOs, mostly NEO candidates from the MPC's NEO Confirmation Page. Lightcurve observations are aimed to derive rotational properties of NEAs and to reveal their possible binary nature. We have derived rotation periods for nearly 100 NEAs during the past seven years, that is more than half of all known NEA rotation periods. We have detected two-period lightcurves that reveal their binary nature for several NEAs. We also provide a support to radar and IR observations of NEAs --- lightcurve data are often an important addition to their data allowing their better interpretation and derivation of better models. As more and more NEAs are to be discovered, the importance of their physical follow-up is expected to further increase, and we plan to continue our lightcurve observations at a rate only limited by a number of available targets and a number of observing nights available to us. A collaboration with other stations doing similar observations has been quite fruitful in past and it is expected to further increase.
Astrometric observations of NEOs are an important complementary program --- since they can often be completed rapidly (normally in several minutes), we can utilize short breaks in photometric series to switch to astrometric observations of NEOCP and other objects in a need of follow-up. The astrometry is also a useful program for (parts of) nights when there is no suitable photometric target on our list. We pay attention to estimating reliable magnitudes of the astrometric targets from the unfiltered images.
Observations within the Ondrejov NEO Programme are done on every (at least partly) clear night throughout each lunation except +/-3 days around full moon when moonlight is too strong. We attempt to maximize our time availability for the NEO follow-up, and we also coordinate our observations with several other European stations through a special NEO Coordination Page that allows us to better allocate observational resources when there occurs too many targets to follow-up on the NEOCP than we can observe at a given time. With a suitable coordination of the follow-up observations with other stations, I believe that we shall be able to comply with a several-fold increase of the demand of follow-up of NEA discoveries up to V=20 to 20.5 (depending mainly on an apparent motion of the objects) in near future. We would appreciate keeping and amending a standard way of exchange of the information on NEO discoveries, best through the MPC's NEOCP to which we have optimized our software. Whenever a new discovery of a potential NEO appears on the NEOCP before or during our observing night, we always put it immediately on a top of our priority observing list and do it at the earliest suitable moment.
The Ondrejov NEO Programme is done in close collaboration with the Astronomical Institute of the Charles University in Prague, co-investigator M. Wolf. The Ondrejov Observatory Asteroid Group currently consists of four people that devote a full or part of their worktime to the project (equivalent 2.8 people): P. Kusnirak and L. Sarounova, observers who do most of the observations (and not only), M. Velen, who develops some key parts of our software, and me as the principal investigator. A couple more people are expected to join us for a part of their worktime in near future. A future advance of our programme is critically dependent on an availability of more financial resources, mostly for people salaries. Among (nonfinancial) rewards to our observers, there is, besides their satisfaction that they contribute to the very interesting field of astronomy, a possibility to propose names for their (accidentally) discovered new (main belt) asteroids; a follow-up of them is therefore a third, supplementary part of our programme being done at suitable moments as allowed by the two main tasks described above.
KLET NEO FOLLOW-UP ASTROMETRIC PROGRAMMEJ. Ticha, M. Tichy and M. Kocer
Zatkovo nabrezi 4
CZ-370 01 Ceske Budejovice
Near-Earth Objects (NEOs) belong to the most fascinating bodies in the solar system. These small bodies have the capability of making close approaches to or even collide with the Earth. The number of known Near-Earth Objects has increased enormously in recent years due to LINEAR and other large surveys (Spacewatch, LONEOS, NEAT and CSS). This discovery process has to be followed by follow-up observations to obtain a sufficient number of precise astrometric data needed for an accurate orbit determination of newly discovered bodies. About forty per cent of the known NEOs have been observed for more than one opposition.
The Klet Observatory has pursued NEO follow-up CCD astrometry since 1994. This follow-up programme covers confirmatory observations of newly discovered NEO candidates, continues over a sufficient observing arc of NEOs in the discovery apparition and also considers testing of newly discovered NEOs for possible cometary activity. A very important part of this programme are NEO recoveries in the second convenient apparition. A special attention is given to the Potentially Hazardous Asteroids (PHAs).
We discuss here methods, techniques and results of the Klet NEO follow-up CCD astrometric programme using 0.57-m telescope. The present magnitude limit of this programme is about V=20 mag. The Klet Observatory is one of the most productive world sites in this field.
We also mention ways for selecting useful and important targets for NEO follow-up astrometry.
Finally we present here a planned extension of Klet NEO programme to fainter objects by means of larger, 1-m telescope, which is being built at Klet now. An increasing magnitude limit of NEO surveys as well as a need for astrometric data for fainter objects (observations in a longer arc, recoveries, cases of "virtual impactors" etc.) shows that NEO observations need more observing time on larger telescopes, and we hope to help.
KLENOT PROJECTM. Tichy, J. Ticha and M. Kocer
Zatkovo nabrezi 4
CZ-370 01 Ceske Budejovice
Considering the critical points of NEO astrometry we have decided to extend the Klet Observatory NEO follow-up programme to fainter objects using a new 1.06-meter reflector equipped with a more efficient CCD camera. This KLENOT Project started in 1997/1998.
The KLENOT project is a project of the KLEt observatory Near earth and Other unusual objects observations Team (and Telescope), concentrating particularly on fainter objects, up to a limiting magnitude of V = 22.0.
The planned main goals of project KLENOT are confirmation and follow-up astrometry of newly discovered NEOs, recoveries of NEOs in the second opposition, and follow-up astrometry of poorly observed NEOs and other unusual objects.
For the proposed project we are building the new 1.06-m KLENOT telescope. We present here the current status of the KLENOT Project.
A NEO SURVEY IN THE SOUTHERN HEMISPHERE: BUSCA - Busqueda Uruguaya de Satelites, Cometas y AsteroidesTancredi G.(1), Sosa A.(1) (2), Acosta E.(2) & Ceretta A.(2)
(1)Depto. Astronomia, Fac. Ciencias, Montevideo, URUGUAY
(2)Observatorio Astronomico "Los Molinos", Ministerio de
Educacion y Cultura, URUGUAY
The surveys looking for Near-Earth Objects have been concentrated up to the moment in the northern hemisphere. None of the existing surveys reach declinations southern than 30deg, therefore more than 25% of the celestial sphere is not covered by any project.
Almost none of this programs include searches in the nearby region to the Sun, instead they generally look at the opposition region. As an important consequence, several NEOs, specially those which orbits interior to the Earth (Atens), are lost; as well as an important portion of the new comets, those coming from the Oort cloud with perihelion distances of the order of 1AU. The only search programs in this region are the amateurs visual searches, principally from Japan, USA and Europe. These programs are dedicated to the search for comets (not asteroids), and its efficiency has remained practically constant since the last century (10 comets per year) since they have not improved the method (visual telescopic search).
Recognizing this North-South asymmetry several groups have urged to build new facilities in the southern hemisphere (e.g. the NASA - NEO Survey Group, the UK Task Force on NEOs, the Spaceguard Foundation, the IAU Working Group on NEOs, etc.).
The Dept. of Astronomy (University of Uruguay) and the Observatorio Astronomico "Los Molinos" (Code 844) have got a small research grant to install a new survey telescope in the countryside of Uruguay (Latitude 34S). The installation of a search program in our latitude will be an important contribution to the discovery of new objects. It is also intended to cover especially the deficiencies of the actual programs, i.e. the region close to the Sun where Aten like objects and long period comets should be found.
We will start our survey with a telescope in the lower range of the already existing surveys, i.e. diameter about 45cm. Software to completely automatize the telescopes will be installed.
The telescope will be installed in a Touristic Ranch in the Province of Maldonado at an altitude of 300m (Long. 55W Lat. 34S). It is a very dark site without public electricity and no populated towns at distance less than 40 km.
We plan to start the observations before the end of 2001.
With a 45cm telescope and a dark sky, we expect to reach a limiting magnitude of ~19 in images without filter. During the main part of the night we plan to cover the region of declinations between -30 and 60deg. Furthermore, in the summer, when we have the better weather, the opposition region in ecliptic reaches -23deg increasing the chances to detect low-inclination asteroids. In the twilight we plan to search for Aten and long period comets. Since the visual amateurs searchs do not reach magnitudes fainter than 12, with a CCD survey we expect to find fainter objects.
Follow-up observations of the discovered objects will be done from the 35cm telescope already installed at the OALM.
Due to the fact that it will be possible to detect objects fainter than in the amateur searches and in consideration to the North-South asymmetry, the installation of a searching program in South America will be an important contribution in the number of discoveries as well as it will succeed in mending in part the present selection effects.
NEO FOLLOW-UP AT MAUNA KEA OBSERVATORYD. J. Tholen, University of Hawaii
The following facilities are available at Mauna Kea Observatory for astrometric follow-up of NEOs. The University of Hawaii 2.24-m telescope has two CCD cameras, a Tektronix 2048x2048 device offering a 7.5 arcmin field of view at the f/10 Cassegrain focus of the telescope, and a mosaic incorporating eight Loral 2048x4096 devices (8192x8192 overall format) that covers about 19 arcmin. Single exposure limiting magnitude for the former device is dependent on the seeing, but has reached about V=24.5 under excellent conditions. The mosaic camera currently has thick chips, therefore the quantum efficiency isn't as high as for the Tektronix device, with a correspondingly brighter limiting magnitude of about V=23 under good conditions. The camera will be upgraded with thinned chips in the coming months. We also have a proposal to the National Science Foundation for a focal reducer, whose design would increase the field of view of the mosaic camera to about 32 arcmin. The telescope itself has excellent non-sidereal tracking capabilities and can theoretically track on an object moving several hundred arcsec per sec. In practice, the fastest object observed with the new control software was moving a little over 1 arcsec per sec (2001 EC16 on 2001 March 24). An autoguider is also available, though limits on the movement of the pick-off mirror could restrict the length of an exposure on a sufficiently fast moving object. However, unguided exposures of 300 sec duration have yielded excellent results. Recent follow-up observations have pushed the telescope to its software zenith distance limits of 75 deg (about 3.8 airmasses). Given adequate manpower, this telescope could be used for NEO follow-up observations for at least two nights a month.
The Canada-France-Hawaii Telescope has a mosaic camera with twelve thinned Lincoln Labs 2048x4096 devices (12288x8192 overall format) that subtend 42x28 arcmin at the telescope's prime focus. Readout time is 50 sec when using no binning and 20 sec when binned 2x2 (producing an effective pixel size of 0.4 arcsec). The single exposure limiting magnitude is about 26. Due to heavy demand on this large-aperture telescope, opportunities to do follow-up astrometry are limited.
The Subaru telescope is still in its commissioning phase. The primary wide-field imaging device, SuPrime, is currently undergoing an upgrade to its detectors. Ten thinned Lincoln Labs 2048x4096 devices (10240x8192 overall format) provide a 30x24 arcmin field of view at the telescope's prime focus. The expected limiting magnitude should be fainter than 27. It is unlikely that this system would be allocated for routine follow-up work, but for special cases, such as those involving objects with non-zero collision probabilities, one can expect that a compelling scientific case could be made for sufficient telescope time to perform the observation.
During my presentation, I will summarize recent follow-up activities utilizing the facilities above. Since 2000 November, heavy use has been made of the Spaceguard Central Node's "Menu of Opportunities" to select objects that utilize these facilities to best advantage. Through March, approximately 50 objects fainter than magnitude 20 have been selected from this list and successfully observed. The principal reason for a failed observation has been due to crowded star fields at low galactic latitude.
STATUS OF NEO INITIATIVES AROUND THE WORLDAndrea Carusi, President, The SPaceguard Foundation
The status of on-going or planned initiatives concerning NEOs is reviewed in this presentation. Particular attention is given to international initiatives involving major international organizations. Both scientific and political initiatives are considered, including approved and/or proposed space missions. The current and future activities of The Spaceguard Foundation are also examined, and its future role discussed.
NEO FOLLOW-UP COORDINATION ACTIVITIES OF THE SPACEGUARD CENTRAL NODE: RESULTS AND GENERAL RECOMMENDATIONSAndrea Boattini, Germano D'Abramo and Giovanni Valsecchi
I.A.S - Planetologia, Area di Ricerca CNR,
via Fosso del Cavaliere 100, I-00133 Roma, Italy.
In the past year and a half the Spaceguard Central Node (SCN) has provided support for the astrometric follow-up activities of Near Earth Objects (NEOs), in particular of newly-discovered objects. Several services, updated on a daily basis, have been developed: the most important is the Priority List, which classifies the need to observe newly-discovered NEOs, into four categories. Following these suggestions, the relative number of lost NEOs has been significantly reduced. In order to address the impact hazard more accurately, we have also organized several campaigns regarding targets with non-zero collision probabilities, thanks to the feedback supplied by the teams involved in collision predictions: this has also included targeted observations of several virtual impactors for1998 OX4, currently the biggest such lost NEO. The recent case of 2000 SG344 has demonstrated the need of such targeted work, and, once more, the need for all the programs to save their own archives: CCD archival resources promise to offer the information that the photographic ones cannot. A recent feature of the SCN is a general monitoring of both search and follow-up activities: a monthly summary report provides suggestions for improving current and future efforts.
NASA'S NEAR-EARTH OBJECT PROGRAM OFFICEDonald K. Yeomans, Ronald C. Baalke, Alan B. Chamberlin, Stephen
R. Chesley, Paul W. Chodas, Jon D. Giorgini, Michael S. Keesey
( JPL/Caltech, Pasadena, CA, USA) and Ravenel N. Wimberly (User
Technology Associates, Inc., Pasadena, CA, USA).
In early 1999, NASA established its Near-Earth Object Program Office at the Jet Propulsion Laboratory, with the stated objectives to:
* Facilitate communications within the observing community and between the community and the public with respect to any potentially hazardous objects.
* Establish and maintain a catalog of Near-Earth Objects (NEOs) and provide information on their future close Earth approaches and Earth impact probabilities.
* Help coordinate ground-based observations in order to complete the Spaceguard Goal of discovering 90% of the Near-Earth Asteroids (NEAs) larger than one kilometer within a ten year period.
* Support NASA Headquarters in coordinating with other government agencies and with foreign governments and international organizations on NEO issues.
* Develop and support a strategy and plan for the scientific exploration of NEOs including their discovery, recovery, ephemerides, characterization, in-situ investigations, and resource potential.
Significant progress has been made on all of these objectives. An award winning interactive NEO web site has been established (http://neo.jpl.nasa.gov/) to communicate information to the scientific community and public. An automatic update process has been established for all NEOs. As new astrometric data become available for a particular NEO, its orbit is automatically updated and future close Earth approach circumstances determined - including impact probabilities when appropriate. At timely intervals, metrics are generated and displayed on the web site to track the contributions of each NASA supported search site toward meeting the Spaceguard Goal. Significant efforts to coordinate the nightly search for NEAs within the United States have been undertaken and efforts to further coordinate these NEA search efforts are underway. In an effort to facilitate the coordination of NEO activities on an international scale, fruitful interactions have taken place with personnel of the British Task Force, the Spaceguard Foundation, the Japanese Spaceguard Foundation and the international Organization for Economic Cooperation and Development (OECD).
NEO RESEARCH AND THE IAUHans Rickman, Uppsala Astronomical Observatory
(IAU General Secretary)
Since 1998 the IAU has taken a much more active role than previously in supporting NEO research initiatives on the international scale as well as facing its responsibility, as the world's leading international organization of professional astronomers, to deal properly with informing society and the public about the results - including such that may cause concern. While I believe that significant progress has been achieved, in part within the framework of the Working Group on Near-Earth Objects that will not be covered in detail in this talk, much surely remains to be done. I will present a survey of ongoing initiatives where the IAU takes part, aiming to emphasize a broadening perspective of its involvement.
MISSIONS TO NEO, THE MUSES-C AND INTERNATIONAL COLLABORATION PERSPECTIVEJun'ichiro Kawaguchi,
The Institute of Space and Astronautical Science (ISAS),
3-1-1 Yoshinodai, Sagamihara, Kanagawa 229-8510, Japan.
As the number of Near Earth Objects (NEO) has increased through the recent intensive and extensive search efforts, while the potential impact of them to the Earth has raised not only scientific but also social and cultural concern, there are proposed direct missions opportunities to those objects, which the specialists believe provides the intimate and straight forward information on how those objects has evolved and what material those are made of. As a concrete incarnation of them, the Institute of Space and Astronautical Science (ISAS) of Japan started its great challenge that the human has ever embarked on, the MUSES-C, the world's first sample and return mission from extra terrestrial objects. What made the MUSES-C mission enabled derives from not only the innovative high efficiency electric propulsion system aboard but also the recent discovery and identification of the NEO objects.
The Earth history itself is that of the NEO objects impacts, and in other words, the inspection, analysis and examination of those Near Earth Asteroids and Comets are sure to disclose some key clues to the questions of where the ocean comes from and where the life is originated and the like. The only information available so far in regard to those questions is the meteorites on the ground and the telescopic and remote observation of those objects that are seen as one point in the sky. Therefore, the direct visit to those objects does connect the correlation between those two and will be extended to understand about much more objects in the solar system.
However, in view of the technological aspects on the sample and return have still a lot of difficulties which have prevented from realization until today. Those are, as already mentioned, the revolutionary electric propulsion, the highly autonomous guidance and navigation function, the surface sample collection method and the recovery method. As a result, the engineering demonstration of those new technologies is essential and the MUSES-C is about to be launched one year ahead of today. The author believes the mission does open the new type of interplanetary exploration door and will contribute to understanding even the social and cultural aspects of having the NEO closely flying with our Earth.
The paper presents, first of all, the MUSES-C project time line and its development and current status. The spacecraft is launched in November to December of 2002 and accumulates the orbital energy via what we call the Electric Delta-V Earth Gravity Assist technique including the Earth swing by on May of 2004, making a rendezvous with the asteroid in summer of 2005, leaving the asteroid for Earth in the end of 2005, followed by the sample recovery on the Earth in June of 2007. The round trip flight period is four and a half years. Every flight hardware has been already fabricated and ready now and the flight model integration starts from December of this year. The mission, while it is an engineering demonstration mission, carries the scientific instruments aboard, which are visible camera, near infra-red spectrometer as well as X-ray fluorescent spectrometer in addition to the laser altimeter and the sample collector. The spacecraft releases its robotic lander on the surface.
The project has developed the tight collaboration with NASA of United States from the moment the project started in 1996. From the engineering point of view, ISAS had to develop the thermal protection system for the reentry capsule and the ISAS deep space antenna cannot have a long time tracking of the spacecraft due to the geographical reason. Talking about the scientific aspects, ISAS thinks that having the NASA scientists participate in the sample analysis is the complementary benefit to ISAS, and NASA thinks participation in the orbiter carried instruments has benefit to it. Currently, both NASA and ISAS have established the collaboration frame and are working together toward the joint effort. For this purpose, the joint science working group was built two years before and has been held annually or on request.
The science information that may be obtained through the mission is very precious to the world. And as the story above indicates, this kind of project consists of very sophisticated technologies. It should be stressed that every mission like the MUSES-C had better look for the international collaboration as much as possible to these aims. When the spacecraft is sent to the comets that may preserve the original intact material in its nuclei, the information provided will advance the human being knowledge in a wide variety fields. The paper discusses what kind of exploration scenarios may be found and will give the perspectives on the international collaboration structure as for the missions foreseen to the NEOs.
NEOs AND THE MINOR PLANET CENTERBrian G. Marsden, Harvard-Smithsonian Center for Astrophysics,
Cambridge, Massachusetts, U.S.A.
Following the receipt of reports of candidate NEOs by the Minor Planet Center, tentative ephemerides and their uncertainties are placed in the internet on The NEO Confirmation Page (NEOCP). These ephemerides are revised as follow-up observations are received, and when an orbit computation is reasonably assured, and it is tolerably clear whether the object is asteroidal or cometary, the MPC designation, full complement of observations, credits to the observers and orbital elements accompany an updated ephemeris on a Minor Planet Electronic Circular (MPEC). The NEOCP also notes the disposition of the NEO candidates, including those deemed lost or not to exist, with in the cases of real and confirmed objects the correspondence of the temporary and MPC designations and reference to the MPEC number, if relevant. As yet more follow-up observations are received these and further revisions to the orbital elements are included in the Daily Orbit Update MPECs. Another detailed MPEC is also issued when observations of a given NEO are located at a second opposition, whether found by identification, precovery or recovery. Definitive documentation of the information is contained, as appropriate, in the monthly Minor Planet Circulars (MPC), the (currently) twice-monthly Minor Planet Circulars Supplement (MPS) and the monthly Minor Planet Circulars Orbit Supplement (MPO), as well as in the Minor Planet Center's databases of astrometric observations, orbital elements and identifications.
COLLISION PROBABILITY COMPUTATION USING BAYESIAN PROBABILITIESK. Muinonen (1,2), J. Virtanen (2), M. Kaasalainen (2),
and T. Laakso (2)
(1) Observatory of Turin, Pino Torinese, Italy
(2) Observatory, University of Helsinki, Finland
We compute collision probabilities based on the true six-dimensional orbital-element probability density, that is, the full solution of the statistical inverse problem of astrometric observations. The highlights include the general nonlinear assessment of the 1997 XF11 Earth-collision probability in 2028: using maximum likelihood collision orbits, that is, best-fit orbits that allow a collision, the collision probability turned out to be negligible. Furthermore, we succeeded in computing a fully six-dimensional collision probability for asteroid 1998 OX4 with a strongly non-Gaussian orbital-element probability density. Although 1998 OX4 is currently lost, the collision solutions have been eliminated by negative observations coordinated by the Spaceguard Central Node. Our orbit computation techniques are under constant development: recently, we have put forward a general computational technique entitled statistical orbital ranging, have pointed out that without securing the invariance of the non-Gaussian orbital analyses, the collision probability may be off by a factor of several, have developed methods for the evaluation of the so-called linear approximations, and are developing fast numerical integrators particularly suitable for collision probability computation. We review the various computational techniques, covering linear and nonlinear approximations and the essentially rigorous statistical ranging technique.
AN ANALYTIC THEORY OF RESONANT RETURNSG.B. Valsecchi
IAS-CNR, Roma, Italy
An important aspect of NEO monitoring is the possibility to predict the location, shape and size of impact keyholes. In Italy, over the last two years, an extension of Opik's theory of close encounters has been developed, by the explicit introduction of the nodal distance and of a time coordinate. Assuming a keplerian unperturbed heliocentric motion between consecutive close encounters it is possible to compute the initial conditions for an encounter as functions of the outcomes of a previous one; in this way a completely analytical theory of resonant returns is obtained. It turns out that the initial conditions of a close encounter that lead to a resonant return lie close to easily computable circles on the b-plane of that encounter. With the further assumption that the nodal distance varies uniformly with time, due to secular perturbations, the location, shape and size of impact keyholes can be computed.
THE ESA OPTICAL SURVEY FOR SPACE DEBRIS IN THE GEOSTATIONARY RINGT. Schildknecht(1), R. Musci(1), M. Ploner(1), S. Preisig(1),
J. de Leon Cruz(2)
(1) Astronomical Institute, University of Bern, Sidlerstrasse 5,
CH-3012 Bern, Switzerland
(2) Instituto de Astrofisica de Canarias, 38200 La Laguna,
It has been suspected since a long time that the geostationary ring may contain a population of small debris objects. The current catalogue population, e.g. from the US Space Command catalogue, is, however, limited to objects larger than about 1 m2. In view of this situation, several space agencies started to perform optical observations of the GEO ring under the auspices of the Inter-Agency Space Debris Coordination Committee (IADC). The European Space Agency (ESA) initiated its own program for optical observations of space debris using a 1 m Ritchey Chretien telescope on Tenerife (Canary Islands).
After a first test survey of 13 nights in 1999 the ESA telescope is routinely used for GEO surveys since January 2001. We will present the search strategies, the object detection and data reduction procedures of the surveys. The results clearly confirm the substantial population of small objects in the size range from 1 to 0.1 m which was first detected in the 1999 test survey. Furthermore for the first time a clear signature of 'clouds' of faint objects has been seen which can be most easily explained by single sources or events.
OVERVIEW OF NASDA'S ORBIT ANALYSIS SYSTEM - FOR A CASE OF SPACE DEBRISKazuaki Nonaka, Mikio Sawabe(NASDA), Takao Yokota(JSF),
Syuzo Isobe(JSGA), Nariyasu Hashimoto(JSGA), and Masaya
NASDA requests the Bisei Spaceguard Center (BSGC) to observe space debris for the purpose of an investigation of space debris environment. BSGC is developed by Japan Space Forum, and operated by Japan Spaceguard Association.
NASDA has acquired observation data of space debris obtained by BSGC since February 2000, and has developed an orbit analysis system for space debris for the debris observation and determination.
At present some geostationary objects are regularly observed and some objects on transfer orbit and low earth orbit (LEO) are experimentally observed. One of the experimentally observations, MIR the Russian space station was carried out a controlled de-orbit last March, was observed using simple observation system at BSGC. As a result of the MIR's orbit determination using observation data for three days, we ware confirmed that the determined orbit is useful for an orbit prediction to track the MIR from BSGC.
On the other hand, NASDA will launch the Laser Ranging Equipment (LRE) in this summer that has 50cm in diameter and will be injected into a transfer orbit. So we will observe LRE at BSGC for a study of small satellite visibility and the orbit determination.
In the near future, we will survey all the zone around GEO observable from BSGC. Then we will be able to put about two hundred geostationary objects in a catalog. On the other hand, we have a plan to make coordinated observation programs using both of BSGC and KSGC. KSGC is the Kamisaibara Spaceguard Center, a radar observation facility at Kamisaibara, will be ready for operation in 2003.
This paper shows an overview of NASDA's orbit analysis system, some results of orbit determination for space debris and Ideas of BSGC future observations.
RECENT STATUS AND EVALUATION OF NASDA ORBIT DETERMINATION SYSTEM - FOR A CASE OF SPACE DEBRISMasafumi Yoshimura, Masaya Kameyama, Shiro Ishibashi (Fujitsu Ltd.)
Kazuaki Nonaka, Mikio Sawabe (NASDA),
Syuzo Isobe, Nariyasu Hashimoto (JSGA)
and Takao Yokota(JSF)
Japan Space Forum (JSF) is now constructing two kinds of facilities for observing Near Earth Objects (NEO) and space debris. Optical observation using telescopes with diameter of 0.5m and 1m is performed at Bisei Spaceguard Center (BSGC), and operation with 0.5m telescope has already started since 2000.
A phased array radar equipment of Kamisaibara Spaceguard Center (KSGC) will be completed in 2003. By using these observation data, National Space Development Agency of Japan (NASDA) has a plan to determine the orbit of space debris.
Optical and radar observation data are transferred to the data processing center at Tsukuba Space Center (TKSC). At TKSC these data are used for orbit determination, and resultant orbital elements are stored in a database.
From orbital data, observation planning and orbit prediction are performed, and these results are used for the next observations at BSGC and KSGC.
For this one and a half year, NASDA has evaluated orbit determination results using optical data from BSGC. A few days observation data give a sufficient orbit determination precision in case of near-geostationary objects.
Residuals of observed angle data after estimation are consistent with the seeing size of optical data. These results show the quality of observed data from BSGC and the validity of the orbit determination system at TKSC.
In this paper the outline of NASDA orbit determination system is described, and typical results of orbit determination of near-geostationary objects are presented.