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April
2005
30 April 2005 - Saturday
Risk monitoring: April closes out with a Daily Orbit Update (DOU) MPEC today reporting no observations of objects with impact solutions. Yesterday's DOU showed that Pla D'Arguines Observatory in Spain caught 2004 MN4 the night before, adding twenty-plus days to the observation arc, and yesterday NEODyS very slightly changed its risk assessment.
April
2005
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28 April 2005 - Thursday
Risk monitoring: Today's Daily Orbit Update MPEC reports that 2005 GF81 was caught yesterday and the day before with the Australian National University 1m telescope at Siding Spring. Only JPL had listed this object as a risk, and today removed it. It was one of three objects mentioned as going unreported in A/CC news of the 22nd below. Of the other two, 2005 GQ33 has now gone technically out of view without further observation.
NEODyS today reorganized its Risk page, moving eleven objects no longer in view into categories identified as lost or too small to cause ground damage.
April
2005
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27 April 2005 - Wednesday
Risk monitoring: Until a couple of odd items popped up today, there had been no risk monitoring news to report since April 20th (see report below). First, today's Daily Orbit Update MPEC reported observation of 2004 MN4 from more than four months ago, from Schiaparelli Observatory in Italy on January 15th, and today NEODyS very slightly raised its risk assessment.
Object | Monitor |
Years | VI | PS cum |
PS max | T S | Arc days |
| 2001 AV43 | NEODyS before | 2066-2067 | 2 | -4.54 | -4.62 | 0 | 182.438 |
| NEODyS today | 2049-2072 | 6 | -4.93 | -5.04 | 0 | 182.438 | |
| JPL today | 2066-2097 | 6 | -4.82 | -5.03 | 0 | 182.438 | |
|
VI = count of "virtual impactors" (impact solutions) | |||||||
April
2005
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24 April 2005 - Sunday
Comet news: Not really news by now, but, just for the record, two distant comets have been discovered since A/CC last reported comet news on March 15th:
| Comet | Discovery MPEC | q | TP | i | |
|---|---|---|---|---|---|
| P/2005 GF8 (LONEOS) | 2005-G88 of 13 April | 2.823 | 2005-08-11.663 | 1.2° | |
| C/2005 G1 (LINEAR) | 2005-G23 of 4 April | 4.965 | 2006-02-26.523 | 108.4° | |
| TP is time of perihelion. Perihelion distance q is the closest the comet comes the Sun, given in astronomical units (AU). Earth averages 1.0 AU from the Sun, Mars 1.52 AU, and Jupiter 5.2 AU. Inclination i is the angle of the object orbit's plane to the plane of Earth's orbit, and anything past 90° is "retrograde" — coming around the Sun against the orbital direction of planets and most asteroids. TP, q, and i here are from the latest update rather than discovery MPECs. | |||||
According to the SOHO comet discovery chat page on April 15th (message now scrolled off, see archive), Rainer Kracht's 150th SOHO discovery is C2000 V4 (SOHO-942). He has posted a page about how another of his discoveries, C/2001 T5 (SOHO-359), followed a very similar path eleven months later. See also MPEC 2005-G93.
JPL's Steven Chesley told the Minor Planet Mailing list (MPML) in late March that his analysis of comet 9P/Tempel 1 observations seemed to show "a tailward bias of a half arcsecond or more. Most astrometric reduction software identifies the comet's centroid by fitting a radially symmetric (gaussian) point spread function. But for a comet, coma asymmetry (i.e., the tail) will pull the symmetric PSF tailward from the true peak, thus biasing the observation. We have seen this before with other mission targets, such as [19P/Borrelly] and [81P/Wild 2]." A solution, he said, is to "to use a very small aperture around the peak when fitting the PSF ... a radius of 2-4 pixels around the peak of the PSF should be sufficient, and he asked that observers using a debiasing technique for reporting positions for this comet let him know.
Bits & pieces: Martin Mobberly in England has put up a new Web site for his Cockfield Observatory and other observing locations, with images of comets and asteroids, and a lot more.
Jim Gamble has posted to his Latest El Paso Event page a JPEG image and QuickTime movie of a bright meteor caught at 1:37am MDT on April 13th from his home in west Texas.
The April edition of Distant EKOs has been posted, apparently on the 14th, which now puts this online publication on a schedule to appear in even-numbered months (the previous edition came in January). It includes abstracts of papers, many with preprint links, on topics such as the shaping of the Edgeworth-Kuiper Belt, the nature of the belt's smaller members, how an extended scattered disk might have been formed, and the Pluto-Charon system (three papers), as well as one about "Neptune Trojans as a Testbed for Planet Formation."
Risk monitoring: Yesterday and today's Daily Orbit Update MPECs reported no observations of objects with impact solutions, and, at last check, there is no other risk monitoring news to report. This is normal at the time of the full Moon.
April
2005
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22 April 2005 - Friday
Risk monitoring: To catch up on reporting the narrative of four days of risk monitoring news, it is easy to start with yesterday and today, which had almost no news. Tuesday's Daily Orbit Update (DOU) MPEC reported observation of 2005 GN59 from Junk Bond Observatory in Arizona from the morning before, and 2005 GN59 was reported in the next DOU from UKAPP in Northern Ireland using the Faulkes Telescope North in Hawaii on Tuesday. NEODyS removed its impact solutions for this kilometer-size object on Tuesday and JPL on Wednesday.
Wednesday's DOU also carried observations of 2005 GC120 from UKAPP/Faulkes North on Tuesday and 2005 GK141 from Mt. John Observatory in New Zealand on Monday. And NEODyS and JPL removed all impact solutions for these two objects on Wednesday. 2005 GK141 is a small object, estimated at 130 meters/yards wide, and 2005 GC120 is perhaps 380 meters in diameter.
Regular A/CC readers know that discovery and observation of potentially hazardous objects slows during the time of the full Moon, so it was nice work that led to three PHOs having all of their impact solutions removed early this week. Meanwhile, it is interesting to take note of three other objects with impact solutions that are currently in view but lack follow-up and, like other risk-listed objects in recent months, are missing from the European Spaceguard Central Node's Priority List. 2005 GQ33 is a small object (perhaps 60 meters in diameter) listed by NEODyS and JPL that hasn't been reported observed since its April 7th discovery announcement. 2005 GF81, an object estimated at 380 meters wide and listed only by JPL, hasn't been reported since its discovery was announced April 11th. 2005 GY8 is about 190 meters wide and is listed by both risk monitors. Its discovery was announced on April 4th, and observation has been reported once since then, in the DOU of 13 April.
Yesterday's DOU reported 26-27 March and 1 and 6 April radar observations of 2005 EU2 that were first published on April 6th and that resulted in NEODyS and JPL removing all of their remaining impact solutions that day for this object, which is estimated at about 80 meters wide. The DOU also reports further radar observations from Goldstone in southern California on 7 and 9 April.
April
2005
18 April 2005 - Monday
Risk monitoring: Today's Daily Orbit Update MPEC reports a sweep of 2005 GC120, 2005 GE59, and 2005 GN59 by UKAPP in Northern Ireland using the Faulkes Telescope North in Hawaii yesterday, along with the Spacewatch 0.9m telescope which observed 2005 GE59. Today NEODyS and JPL eliminated their last single impact solutions for 2005 GE59 and lowered their risk assessments for both 2005 GC120 and 2005 GN59.
April
2005
17 April 2005 - Sunday
Risk monitoring: Today's Daily Orbit Update MPEC reported that Great Shefford Observatory in England observed 2005 GK141 early this morning UT. NEODyS has now posted this small object with a risk assessment similar to JPL's, which was revised downward today.
April
2005
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16 April 2005 - Saturday
Risk monitoring: JPL has posted with two low-rated impact solutions 2005 GK141 that was announced today in MPEC 2005-H03 as discovered on the morning of the 13th by LINEAR in New Mexico, which also caught it the next morning. This small object was confirmed this morning by Three Buttes and Sabino Canyon observatories in Arizona, Cordell-Lorenz Observatory in Tennessee, and Table Mountain Observatory in southern California.
Today's Daily Orbit Update MPEC carries observations from yesterday morning of two objects with impact solutions: 2005 GE59from the Spacewatch 0.9m telescope and 2005 GN59 from Jeffrey Sue using Rent-A-Scope at New Mexico Skies. Today JPL reposted 2005 GE59 with a single low-rated impact solution in 2010, and NEODyS reduced its risk assessment to one even lower-rated solution in 2059. And NEODyS lowered, and JPL slightly, lowered overall risk ratings for 2005 GN59.
April
2005
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15 April 2005 - Friday
Risk monitoring: Today's Daily Orbit Update (DOU) MPEC reports observation of 2005 GC120 from Farpoint Observatory in Kansas yesterday morning and early today from Great Shefford Observatory in England. Today JPL cut its impact solution count for this object from 1,076 to 144, and NEODyS went from 743 to 55, with both removing any solutions before 2017 and lowering their overall risk ratings. The DOU also has positions reported for 2005 GE59 from Spacewatch 0.9m telescope in Arizona. Only NEODyS still has this object still listed, and today it further lowered its risk assessment.
Monitor |
Years | VI | PS cum |
PS max | T S | Arc days | |
| 1997 UA11 | NEODyS before | 2053-2053 | 1 | -6.21 | -6.21 | 0 | 9.953 |
| JPL before | 2053-2073 | 2 | -6.34 | -6.36 | 0 | 9.953 | |
| NEODyS now | 2073-2073 | 1 | -6.93 | -6.93 | 0 | 12.938 | |
| JPL now | 2073-2073 | 1 | -7.06 | -7.06 | 0 | 12.938 | |
| 2002 TY59 | JPL before | 2074-2084 | 2 | -6.88 | -6.88 | 0 | 25.871 |
| JPL now | 2074-2084 | 2 | -6.84 | -6.84 | 0 | 25.871 | |
|
VI = count of "virtual impactors" (impact solutions) | |||||||
The DOU yesterday had one object in current view with impact solutions, 2004 MN4 from 3, 5, 9, and 10 February from Pulkovo Observatory near Saint Petersburg, Russia. And NEODyS yesterday very slightly raised its risk assessment.