August 2002 Asteroid/Comet News
Updated: 11 July 2004
<<July 2002 News ^UP^ September 2002 News>>
SpaceRef.com posted two 6 Aug. NEO News letters from David Morrison. One briefly covers the Asteroids Comets Meteors (ACM) conference just held in Berlin, including what may be a new understanding about reflectivity differences in asteroids according to size. Another gives some "Last words on NT7."
The 5 Aug. issue of Tumbling Stone also has some words about NT7 news coverage and a brief report on ACM '02, including this: "most of the dust contained in the zodiacal bands originates from a single, comparatively recent event in the Veritas family."
Space.com's 7 August report about NASA trying to close down its VASIMR plasma rocket program spends much of its second page talking about using such a rocket for asteroid deflection, as advocated by VASIMR head and astronaut, Franklin Chang-Diaz, and by astronaut and NASA official John Young.
The American Physcial Society Tip Sheet of 7 August tipped the news media to a new scientific paper out of the Sloan Digital Sky Survey that is awaiting publication at the Astronomical Journal. The paper by Zeljko Ivezic et al. reports that a survey of the colors of more than 10,000 asteroids shows that the four main families of asteroids represent four main color types. The distinct optical colors indicate that each family has a different origin but the similarities within a family suggest that each family comes from one source. Over 90% of asteroids are thought to belong to color-segregated families. The preprint is available as a 282Kb PDF from the Los Alamos preprint server, and also from the lead author's references page as a 1Mb PDF. (The larger version has figures at a readable resolution.)
The 27 June Tumbling Stone issue #15 told about six NEO mission proposals that the European Space Agency has selected for preliminary study. They include concepts such as close-up radar inspection of asteroid interiors, landers, space-based surveys, and first steps toward developing deflection techniques. One of these, the Spanish/German Don Quixote mission spearheaded by Deimos Space to do research on asteroid deflection, is written up in a BBC 9 August article.
The 500th SOHO comet was announced on 14 Aug. to be C/SOHO-500 (2002 P3). This comet was reported in MPEC 2002-P63 the following day, but note that the IAU and CBAT/MPC office do not use the SOHO staff-issued SOHO### name extensions. It is a faint object found 12 Aug. by science teacher Rainer Kracht of Germany in images available over the Internet from the SOHO solar observatory. (He is one of the leading searchers for SOHO comets, with 63 discoveries to his credit, and a family of "sungrazers" was named for him after he noted their orbital similarities.) See the NASA/Goddard news release, and Space.com and MSNBC had reports on 14 Aug., as did Astronomy.com, CNN, and ESA on the 15th.
On Seiichi Yoshida's returning Comets Waiting for First Observation page, he reports that "118P/Shoemaker-Levy 4 was observed on August 19th at 18.6 mag, but not yet officially announced." This is its third apparition, and was last seen in 1998. See Yoshida's 2002-04 page with finder charts and light curve estimate.
In its 21 August updating of Discovery Circumstances, the IAU Minor Planet Center added 2,790 new asteroid numberings, now topping out at 46511 4356 T-3. No new namings were announced.
LINEAR on 16 August discovered a very interesting small object (on the order of 500 meters/yards across) that initial observations indicate has a perihelion inside Mercury's orbit and a semimajor axis inside Earth's orbit, but an eccentricity that puts its aphelion nearly on top of the orbit of Mars. For more about 2002 QY6, see its announcement in MPEC 2002-Q17 of 21 August and JPL's Orbit Viewer.
LINEAR, which discovered 2002 LY45 on 14 June, has found precovery images from June 14th two years ago, as reported in the Minor Planet Center's formatted Daily Orbit Update for 24 August. As you may remember, JPL and NEODyS had LY45 rated at Torino Scale 1 up through the 4th of July.
Klet Observatory has posted a 25 August report and pictures on how Europe's historical flood has affected their operations and staff in Ceske Budejovice, although not the observatory itself (on Klet mountain). Updated 15 October 2002.
For awhile, beginning 17 July, 2002 KK8 was in the Urgent category on the Spaceguard Priority List for experienced observers with telescopes able to reach magnitude 20.5, trying to keep this object from becoming "lost" after it disappears from view in late August. Its priority was later downgraded to "necessary," where it remained until elevated again to "urgent" on 20 August, and ultimately removed on the 26th.
2002 PE130 was discovered on 14 August by LINEAR and on Saturday the 17th was announced by the MPC and went onto the JPL Risks page. On Sunday, the 18th, it also appeared on the NEODyS Risk page, where it remained until the 22nd. JPL pulled PE130 on the 27th in the first update of its pages since 22 August.
Knock one more off of Seiichi Yoshida's list of Comets Waiting for First Observation. MPEC 2002-Q41 of 28 August announced that P/1992 Q1 (Brewington) was picked up on the 26th and watched again on the 27th and into the early hours of the 28th by Los Molinos Observatory in Uruguay, South America. P/1992 Q1 was last seen on 30 March 1993, and it is now headed for perihelion on 19 February 2003 at 1.59 AU. See Yoshida's P/1992 Q1 finder charts and estimated light curve for 2002-04.
Centaur 2002 GB10, discovered with NEAT's Palomar telescope on 8 April 2002 and announced in MPEC 2002-H11, has been updated with the 29 August MPEC 2002-Q44 based on precoveries found on Palomar 1.2m plates from March 1997, and from NEAT's Palomar and Hawaiian instruments in April 2000, March 2001, and during January through April this year.
The Astronomical Journal September issue has an article by Scott S. Sheppard and David C. Jewitt on "Time-resolved photometry of Kuiper Belt objects: Rotations, shapes, and phase functions," in which the authors present "a systematic investigation of the rotational light curves of trans-Neptunian objects based on extensive optical data from Mauna Kea" and combined with a larger sample of light curves from the literature. The preprint is available as a 4.5Mb PDF from the lead author, who also has a "Kuiper Belt Object Lightcurves" page.
CNN in a 30 August report informally polls a few scientists on what they think of the recently floated proposal to use, if the need arises, a "giant air bag" to push a minor object off an Earth collision course. This story originates with New Scientist and the idea comes from Oklahoma State University math professor Hermann G. Burchard.
On 3 August the MPC announced 2002 PN, a faint (H=25.2) PHO discoverd by William K. Yeung on the 2nd, two days before it flew past Earth at just over six lunar distances. In this age of automated NEO surveys, this is the fifth* NEO discovered this year by an amateur observer, and the second by Yeung himself. PN appeared on the NEODyS Risk page on the 4th, was removed on the 5th, and came back on the 6th. The JPL Risks page has had it listed since the 5th. JPL's Orbit Viewer shows an orbit rather close to Earth's own.
*The other five NEOs discovered in 2002 by amateurs were 2002 AR129, 2002 BJ2, 2002 EA, 2002 EL6, and, after the above report, 2002 UQ3.
The recovery of 1998 OX4 (8-9 August 2002)
1998 OX4, which had been on the JPL Risks page, and was listed on the NEODyS Risk page as a lost object, has now been recovered. This was announced 8 August 2002 in MPEC 2002-P34, which equates OX4 with an object discovered two days before by NEAT. OX4 is an eccentric Earth-crossing asteroid perhaps 200 meters/yards across that was originally discovered by Jim Scotti at Spacewatch on 26 July 1998. It was observed into the next month and then was not seen again until now. The net result of this recovery is one less object on the risk pages, with JPL removing it the same day.
It was Thursday evening at NEODyS when this correllation was published, and it took until next morning for its list to drop 1998 OX4, an old acquaintance. OX4 played a big role in bringing Andrea Milani, Steven Chesley (now at JPL), Andrea Boattini, and Giovanni Valsecchi at the University of Pisa to develop the "virtual impactor" concept. The year after OX4 was discovered and lost, they said, we have found a solution to the problem raised by 1998 OX4; the same method could be applied to other similar cases of lost potential impactors which might be discovered in the future. In short, the idea is to replace a full recovery campaign, requiring an inordinate amount of observational resources, with a targeted search for only those, among the possible orbital solutions for 1998 OX4, which lead to impacts; we call these the Virtual Impactors.
An example of putting this concept to work came in January 2001 when two Spaceguard observing campaigns successfully failed to find 1998 OX4 on paths that had been projected as leading to possible impact solutions for several different years, especially 2014, thus completely removing those possibilities.
The short saga of 2002 PZ39 (11-13 August 2002)
A little after 10:30pm local at MPC Saturday night, August 11th, MPEC 2002-P47 was issued for 2002 PZ39. This eccentric (e=0.56) and lowly-inclined (i=2) object crosses the orbits of Venus, Earth, and Mars, and is estimated to be about 750 meters/yards wide. It was caught by LINEAR early on the 10th, outward bound from the Sun side of Earth's orbit after slipping past at more than 22 lunar distances. See JPL's Orbit Viewer for more about this object.
2002 PZ39 debuted on the JPL Risks page Sunday morning the 12th in the number two position with more than a hundred possible virtual impactors. Awhile later it appeared on the NEODyS Risk page with a very different single-impactor assessment, all based on 30 observations from a period of less than 17 hours, and all at Torino Scale 0.
Spaceguard on Sunday the 12th posted PZ39 as "urgent" on its Priority List for experienced observers, and Monday morning the number of observations available for crunching by the orbital dynamicists had more than doubled. These 55 new positions came from eight observatories, including more work from Marxuquera, which provided the only new observations available Sunday.
That new data made very quick work of 2002 PZ39, removed altogether from the NEODyS Risk page Monday and down to a single impactor by JPL's reckoning for 2089 (beyond the NEODyS 2080 horizon). With a new batch of 21 observations early Tuesday morning the 13th, that one solution was eliminated and PZ39 was yanked from the JPL Risks page.
But that wasn't all the news for the 13th. A little after 7pm local that Tuesday night at MPC, MPEC 2002-P57 was issued equating 2002 PZ39 with 1995 UQ53, which had been observed 23 and 27 October 1995 by Spacewatch at Kitt Peak.
Perseids 2002 (11-13 August 2002)
For reports about 2002's Perseids peak during the early morning hours of 12 and 13 August, see especially Space.com and Sky & Telescope, and also BBC and CNN, all from 13 August. There are some great pictures on the SpaceWeather.com Perseids 2002 Photo Gallery page, including images and movies from George Varros, who has built a system that tracks meteor movement.
The runup for this year's Perseids included Sky & Telescope's preview with info about photography, including great stuff about stereo imaging and about videotaping Perseid lunar impacts (for more about that, see Brian Cudnik's ALPO Lunar Impacts page). Here are some more previews, observing guides, and info about the shower source, comet 109P/Swift-Tuttle: Science@NASA 7 August and 19 July, Space.com 6 August and 9 August, ESA 9 August, CNN 8 August and 12 August, and BBC 12 August.
The precovery of 2002 HK12 (13 August 2002)
Minor Planet Electronic Circulars appear to be pretty dry reading, and the Daily Orbit Updates (DOUs) might seem to be especially impenetrable, but there is some drama to be deduced from all that formatted data. The starting point is understanding that year-based asteroid designations have two forms, the one you see used in text, like here, 2002 HK12, and the "packed" form used in formatted data, K02H12K. That's always to the left of a data row, or record, and to the right in observation records you will find a three-character observatory code.
2002 HK12 is an interesting example. It was discovered on 30 April 2002 by JPL's NEAT program, and, as reported here at the time, it had a fling on the JPL NEO Program's Current Risks page during 2-3 May. It is estimated to be about 1.3 km. across, give or take 500 meters (so, maybe a mile or less), and has an orbit eccentric enough (e=0.53) to go from the Main Belt to perihelion at 0.9383 AU. Since Earth orbits at 1 AU ("astronomical unit"), HK12 can skim by every now and then as close as about ten lunar distances.
Skim through the DOUs since 2002 HK12 was discovered and you will see that, subsequent to discovery, images from NEAT and LINEAR were found from during 4-12 April, and also that HK12 has been under fairly constant scrutiny since discovery, including July 31st observations at Siding Spring Observatory in Australia. A new orbit was published in the 13 August MPEC 2002-P56 based in part on that work, and also, say the neat rows of terse data, based on just now finding HK12 on Siding Spring plates from 11 June 1985.
The problem with these formatted reports is that they have no place for telling who played the detective. However, European Spaceguard has a page with links to "precovery" programs and astronomical archives that is an excellent starting point for learning more about how some people search for minor objects without a telescope.
Comet 2002 O6 gets a name (17 August)
Comet C/2002 O6, which had remained unnamed since its August 1st announcement, was quietly identified publicly for the first time as C/2002 O6 (SWAN) on 17 August. This is the third comet discovered with the SWAN instrument on the SOHO solar observing spacecraft, and has been tallied as SOHO-497 by SOHO staff, who call the previous two SWAN comets SOHO-93 and -429. However, on the Web site of the International Astronomical Union (IAU) Division III Committee on Small Body Nomenclature there is a page entitled, "Discovered Comets Without Names," and the only two objects on it are . . . the previous comets discovered with SWAN.
Probing Phobos (20 August 2002)
A 20 August AFP report from Moscow on SpaceDaily said that NPO Lavochkin and OKB Kaluga* are working on a Phobos sample return mission.
Lavochkin is most recently known for its multipurpose Fregat "kick" stage and IRDT inflated reentry heat shield, which put together should make the Fregat reusable. The heat shield in several tests is reported to have had only one success, although one or two tests may have been simply lost in the wilderness. One failure involved the Fregat. Another involved the Cosmos 1 solar sail project of the Planetary Society, carried out by Lavochkin's Babakin Space Center, which is moving toward another try soon with a plowshared Volna launch vehicle (see MSNBC 30 Sept. 2002 report).
The Fregat and IRDT technology comes directly out of Lavochkin's work on its last Mars mission in the mid-1990s, which followed a long string of Soviet spacecraft it built to send to the Moon, Mars, Venus, and Halley's Comet, including successful lunar sample return and rover missions. Its two missions to Phobos during 1988-89 each carried a lander (photos), and the second also brought a "hopper." The first mission failed en route to Mars, and the other before the landing attempt, as Jim Oberg recounted in a 30 June 2000 article, and as explained in archival information at NASA/Goddard, NASA/JPL, and UTexas.
The development of technology and techniques for exploring Phobos, an object the size of 433 Eros, has direct application to the exploration of all minor objects. For more about Phobos, and how it is both like and unlike asteroids explored to date, see Space.com's 13 March 2001 Mars moons wrap-up.
*NPO is the Russian acronym for Research/Production Association, somewhat like a corporation, and OKB stands for Experimental Design Bureau.
2002 PD43's comet-like path (12-22 August)
2002 PD43 was removed from the NEODyS Risk page on the 18th and from JPL's Risks page on the 22nd. It was announced on the 12th, when it showed up initially in the top slot on the JPL Risks page.
Chasing 2002 QC7 (22-30 August)
The Minor Planet Center's Daily Orbit Update (DOU) for 29 August showed that Tenagra Observatory in Cottage Grove, Ore. located 2002 QC7 on the morning of the 28th, apparently the first time it has been picked up since early on the 20th. The DOU for the 30th carried observations by three more observatories during 28-29 August, and, early on the 30th, JPL pulled QC7 from its Current Risks page.
Patrolling for fireballs
There is some great information on the Web about "patrolling" for fireballs, a scientifically useful activity that is open to just about everyone interested. A recent example is a Sky & Telescope's 29 July article about Edward Albin's $200 homebuilt and home-mounted system that uses a surveillance CCD camera and a VHS VCR near Atlanta, Georgia.
Chris Peterson's robotic Cloudbait Observatory in the Colorado Rockies, which he uses to study starspot-caused brightness variations in M dwarf stars, also includes a homebuilt all-sky camera to watch for fireballs. See his meteors page. The camera page links to plans and a manual in PDF format for building and operating your own meteor camera, and also links to the Denver Museum of Nature & Science All-Sky Camera Network (ASCN) project for grade-school students across Colorado.
Some snippets about how this community science program is progressing can be viewed on Web pages such as North American Skies' ASCN page of 2001 vintage ("a team of twelve Colorado teachers is developing curriculum in collaboration with the" museum), an item in an October 2001 student newsletter, and a January 2002 note ("It is rare that a research opportunity comes along that involves students so directly") from teacher, Andy Caldwell, whose ASCN and Antarctic work is reported in an April 2002 school newsletter.
Risk concerns removed during August
Potentially hazardous asteroids removed from the NEODyS and/or JPL risk pages during August 2002 include: 1998 OX4 (story above) and 2002 OA22, 2002 NT7, 2002 PB, 2002 PD43 (story above), 2002 PE130, 2002 PR1, 2002 PZ39 (story above), and 2002 QC7 (story above).