Although many nights in November had interruptions from cloud, observing time was logged on 18 nights and there were plenty of Near Earth Objects to be followed that had been discovered during the month by the surveys.
Apollo 2009 VX had been discovered on Nov. 9th by the Catalina Sky Survey (CSS) as a 19th mag. object but had brightened to 17th mag. by the time it was picked up from Great Shefford early on the morning of Nov 12th, moving at 150"/min. It was then at 2.8 Lunar Distances (LD) and would pass at 2.59 LD at 13h UT the same day.
Another relatively bright new discovery was Apollo 2009 VZ and although it didn't get any closer than 15 LD it remained above 17th magnitude for 12 nights, I recorded it at 15th mag. on Nov. 12 & 14th. 2009 VZ was intrinsically about 5 magnitudes brighter than 2009 VX, which translates to 2009 VZ having a diameter about ten-times larger than 2009 VX (approx. 300 meters vs. 30 meters), assuming similar albedos for the two objects.
2009 WJ6 was another CSS discovery from Nov 19th and was followed from Great Shefford later that same day. By then it was already about mag. +17.0, at 2.1 LD and moving at 58"/min. It reached its closest to Earth at 11am UT the next day at 0.46 LD and was reported from the Westfield site of the Astronomical Research Observatory, Illinois three hours before perigee, at a distance of 0.82 LD.
One other close approach Apollo object was 2009 WV51. Discovered at 7am on Nov 23 by the CSS it was due to pass at just 0.39 LD the next day. I picked it up on the evening of Nov 23 at 17th magnitude when it was at a distance of 2.8 LD and moving at 'just' 22"/min. Watching individual images download it was easy to see it rising and falling in brightness by approximately 1 magnitude in just a few minutes, though the lightcurve has yet to be reduced. It was last reported from the Magdalena Ridge Observatory, New Mexico on Nov. 24 at 05:43 UT with the 2.4-m reflector, at a range of about 1.8 LD. It went unobserved from Great Shefford that night at its closest approach due to bad weather, but would have been 14th magnitude and moving at over 1,000"/min in the early evening of Nov. 24.
The probable artificial satellite 9U01FF6 mentioned last month was due back at perigee early on Nov. 28 after being followed for only 44 hours by 7 observatories at the end of October. I started searching for it on the evening of Nov 23 but given a likely positional uncertainty of up to 1°, the waxing Moon only about 30° to the south and the predicted mag. being +21.2 I was not expecting much success. However, it was picked up only 5' from the predicted position and ranging in magnitude from +20.5 up to +18.9, the standard asteroid magnitude formula obviously not providing a good fit for this object! Further positions obtained on three subsequent nights allowed the effect of Solar Radiation Pressure (SRP) to be determined using FindOrb using all the available observations (26 October - 27 November 2009). SRP effectively pushes an object away from the Sun and the smaller the mass and larger the surface area of the object exposed to the Sun, the larger the discrepancy from Newtonian motion may be observed. Without taking into account SRP the RMS residual for 78 positions over the two apparitions is a very unsatisfactory 16", but taking into account SRP this drops to 0.8". The value of SRP (or Area/Mass Ratio) determined was 0.011 m2/kg which is similar to those determined using FindOrb for other distant artificial satellites, e.g.
LCROSS (incl. Centaur) size 14.5m x 4.7m, mass ~3,200kg, SRP = 0.015 m2/kg
IMP8 size 1.4m x 1.6m, mass 371kg, SRP = 0.010 m2/kg
ASTRON (1983-020A) size 6m long, mass 3250kg, SRP = 0.008 m2/kg
and is 10 times larger than the 0.0011 m2/kg value derived for 2006 RH120 (=6R10DB9), the tiny (natural) minor planet that was temporarily trapped in Earth orbit during 2006-2007. All this points to 9U01FF6 being man-made and from a posting on the SeeSat-L (Visual Satellite Observers) mailing list here http://www.satobs.org/seesat/Oct-2009/0176.html it is suggested that 9U01FF6 is very likely to be from a lunar transfer mission of some kind, but the perturbations on the orbit make identification of the specific launch very difficult. It is noted that some of the Agena rockets for the Ranger missions of the 1960s were in very similar orbits.
Sunday, 6 December 2009
Saturday, 31 October 2009
2009 October notes: 2009 TM8, 2009 UD, 2009 UV18, LCROSS and 9U01FF6
Apollo 2009 TM8 made a very close approach to the Earth early on Oct. 17th about 48 hours after discovery by the Catalina Sky Survey. It was followed from Great Shefford from soon after sunset on Oct. 16th when it was moving at an apparent speed of 180"/min, through to 04:20 UT the next morning by which time it had accelerated to 285"/min. It reached its closest to Earth at 03:37 UT at a distance of 0.9 LD. The brightness stayed fairly constant, around mag. +17.5 all night, the decreasing distance from Earth being offset by increasing phase angle but the large increase in apparent speed made it a more difficult target as the night wore on.
Another newly discovered Apollo, 2009 UD passed Earth at 2 LD on Oct. 20 and was observed on the morning of Oct. 17th for 2 hours and again for 3 hours the next morning when it was at about 3 LD and mag +17.0. Over 1,000 images were obtained in those 5 hours and allowed the determination that this ~15 metre diameter object rotates very fast with a period of 83.7 seconds with an amplitude of about 0.7 magnitudes.
2009 UV18 was an interesting LINEAR discovery from Oct. 22, relatively bright at mag. +18 and unusually large for a new discovery, estimated at over 2 km diameter. With a low inclination and the Earth approaching the ascending node of the orbit the size of the orbit was initially rather indeterminate and attempts at trying to identify it with a known minor planet failed, even though it ought to have been relatively bright in earlier apparitions. Then, on Oct. 29, Rob Matson, well known for precovery work with online image databases managed to find it on old NEAT images from Jan 2004, fortunately only 2.5° from the predicted place, even though the uncertainty was estimated at up to 90°.
The orbit of 2009 UV18 is similar to a Jupiter family comet and although it appeared stellar in images taken on Oct.23 and Oct. 26th it is probably worth keeping an eye on as it approaches perihelion this January in the morning sky. The last favourable return appears to have been in May 1993 when it should have reached mag. +16 and before that spring 1976 at mag +17.
The LCROSS mission was followed one final time on the night of Oct 8/9th. The spacecraft was only 6.4° from the gibbous Moon and internal reflections in the telescope made it a difficult target. Unfortunately the sky clouded over before the LCROSS shepherding spacecraft separated from the Centaur at 02:50 UT, the last images obtained that show LCROSS were taken at 01:56 UT but were so light polluted they could not be measured. The image of LCROSS was taken about an hour earlier, before the glare from the Moon became too strong, less than 11 hours before impact with the Moon.
What initially appeared to be a Near Earth Asteroid discovery was reported by the Catalina Sky Survey on Oct 26 and received their temporary designation 9U01FF6. It was 19th magnitude and moving at 10"/min but was already closer to Earth than the Moon. After follow-up from other observatories that same day it was found to be in a very unusual 31.5 day period, highly eccentric geocentric orbit, taking it to within 82,000 km of Earth (0.2 Lunar Distances) at perigee and out to 761,000 km (2.0 LD) at apogee. With an absolute magnitude of +30.9 it would only be 1-2 metres in diameter if it were a natural object, but smaller if artificial (with a higher albedo assumed). Further observations were made from Great Shefford on the evening of Oct. 27th and the last positions reported this perigee came from the OAM Observatory at La Sagra in Spain early on Oct. 28th.
9U01FF6 is fainter than mag. +21 for most of its orbit but will next be at perigee around Nov. 28th and should reach +16th magnitude but moving as fast as 250"-500"/min on the evening of Nov. 27th. Hopefully it will be recovered in the days leading up to that but observability is probably limited at most to only 2-4 nights each perigee. It is likely to be an unusual artificial satellite but further observations at the end of November are encouraged.
Another newly discovered Apollo, 2009 UD passed Earth at 2 LD on Oct. 20 and was observed on the morning of Oct. 17th for 2 hours and again for 3 hours the next morning when it was at about 3 LD and mag +17.0. Over 1,000 images were obtained in those 5 hours and allowed the determination that this ~15 metre diameter object rotates very fast with a period of 83.7 seconds with an amplitude of about 0.7 magnitudes.
2009 UV18 was an interesting LINEAR discovery from Oct. 22, relatively bright at mag. +18 and unusually large for a new discovery, estimated at over 2 km diameter. With a low inclination and the Earth approaching the ascending node of the orbit the size of the orbit was initially rather indeterminate and attempts at trying to identify it with a known minor planet failed, even though it ought to have been relatively bright in earlier apparitions. Then, on Oct. 29, Rob Matson, well known for precovery work with online image databases managed to find it on old NEAT images from Jan 2004, fortunately only 2.5° from the predicted place, even though the uncertainty was estimated at up to 90°.
The orbit of 2009 UV18 is similar to a Jupiter family comet and although it appeared stellar in images taken on Oct.23 and Oct. 26th it is probably worth keeping an eye on as it approaches perihelion this January in the morning sky. The last favourable return appears to have been in May 1993 when it should have reached mag. +16 and before that spring 1976 at mag +17.
The LCROSS mission was followed one final time on the night of Oct 8/9th. The spacecraft was only 6.4° from the gibbous Moon and internal reflections in the telescope made it a difficult target. Unfortunately the sky clouded over before the LCROSS shepherding spacecraft separated from the Centaur at 02:50 UT, the last images obtained that show LCROSS were taken at 01:56 UT but were so light polluted they could not be measured. The image of LCROSS was taken about an hour earlier, before the glare from the Moon became too strong, less than 11 hours before impact with the Moon.
What initially appeared to be a Near Earth Asteroid discovery was reported by the Catalina Sky Survey on Oct 26 and received their temporary designation 9U01FF6. It was 19th magnitude and moving at 10"/min but was already closer to Earth than the Moon. After follow-up from other observatories that same day it was found to be in a very unusual 31.5 day period, highly eccentric geocentric orbit, taking it to within 82,000 km of Earth (0.2 Lunar Distances) at perigee and out to 761,000 km (2.0 LD) at apogee. With an absolute magnitude of +30.9 it would only be 1-2 metres in diameter if it were a natural object, but smaller if artificial (with a higher albedo assumed). Further observations were made from Great Shefford on the evening of Oct. 27th and the last positions reported this perigee came from the OAM Observatory at La Sagra in Spain early on Oct. 28th.
9U01FF6 is fainter than mag. +21 for most of its orbit but will next be at perigee around Nov. 28th and should reach +16th magnitude but moving as fast as 250"-500"/min on the evening of Nov. 27th. Hopefully it will be recovered in the days leading up to that but observability is probably limited at most to only 2-4 nights each perigee. It is likely to be an unusual artificial satellite but further observations at the end of November are encouraged.
Sunday, 11 October 2009
2009 September notes: 2009 SH2, 2009 SN103, 2009 SU104, LCROSS and Herschel
September was a busy time for NEOs, with the Minor Planet Center
Apollo 2009 SH2 was discovered by Gordon Garradd at Siding Spring on Sept. 18th as an 18th mag. object and was due to make a fly-by of Earth within 3 Lunar Distances (LD) by the end of the month. It reached mag +16 when last seen from Great Shefford on Sept. 29th.
Another Apollo 2009 SN103, this one discovered by the Catalina Sky Survey on Sept. 25th was 19th mag., already within 4 LD of Earth and moving at 11"/min. It would reach its closest to Earth (1.2 LD) at about 05h UT on Sept. 28 as it overtook the Earth on its way to perihelion on Oct. 30th. It was observed from Great Shefford 6 hours before closest approach when it had brightened to 16th mag. and had accelerated to a speed of 138"/min. It was also caught the next night in central Gemini, moving slower at 86"/min but with the phase angle increasing very rapidly, it was 18th mag., fading quickly and was a much more difficult target to record.
It is estimated that 2009 SN103 is only about 8 meters in diameter. Another close approach NEO discovered by the Catalina Sky Survey on Sept. 27th and estimated at about 20 meters diameter was 2009 SU104. This Apollo has a very eccentric orbit taking it very close to the orbit of Venus at perihelion, out to 4.2 AU at aphelion. At this apparition it was on its way to perihelion in Nov., crossing the Earth's orbit just after the Earth had passed by. It was observed at its closest at 2.5 LD on Oct 1st when it was mag. 16 and moving east to west at 223"/min in Equuleus.
Several distant artifical satellites were also followed during the month, including LCROSS on Sept. 12th & 16th before it disappeared into southerly declinations until a few days before its impact with the Moon on Oct 9th. The Herschel telescope was also recorded on Sept. 17th at 19th mag. Ephemerides generated from previous astrometry obtained for this object were useless to try and pick it up again as the spacecraft undergoes frequent orbital manoeuvres to keep it near the second Lagrange point (L2). The JPL Horizons ephemeris allowed Herschel to be picked up without problem, moving at 3"/min.
Sunday, 6 September 2009
2009 August notes: 9O0DC57, 2009 QC23 and 2009 QY33
August carried on the very good trend of the first half of 2009, with 18 usable nights providing 96 hours of observing and with plenty of NEO discoveries made by the US based surveys it was a busy month.
On July 30th a fast moving 15th magnitude object found by the Catalina Sky Survey and designated as 9O0DC57 by them was put on the Minor Planet Center's NEO Confirmation page, only to be taken off again the next day with a note "was not a minor planet", normal procedure by the MPC when an artificial satellite is mistakenly picked up as a NEO.
This one though did not match any of the artificial satellites with published orbits. It has a perigee of 18,000Km and an apogee 1/3 the distance to the Moon, making it easily mistaken for a NEO during a close approach.
I followed it over a number of nights during August and on August 2nd managed to determine that it rotates every 5.6 seconds, following it from 00:29 UT into twilight at 03:16 UT. From 00:27 to 01:52 UT it showed a regular 1.5 magnitude variation, but when next picked up at 02:56 UT it was showing a very short flash superimposed on the regular variation, probably less than 1 second long and of about 0.75 magnitudes amplitude. Only about 10 minutes later this flash had increased to about 1.5 magnitudes. The lightcurve is from 495 measurements of 1 second exposures, folded using a period of 5.620 seconds, with the increasing flash marked with curves A and B between phase 0.10 and 0.35. The inset from a 60 second exposure started at 03:21:26 UT shows the object trail 250" long and captures 11 flashes and the secondary maximum can just be made out just to the right of the bright flash.
An 18th mag object moving at 18"/min at discovery and put on the NEO Confirmation page on August 22 turned out to be an very impressive amateur discovery by Noeline Teamo from the Hibiscus Observatory (F84) in Tahiti. Designated 2009 QC23 it was followed at Great Shefford for a week.
Another amateur NEO discovery was made on Aug 27th by the team at the OAM Observatory, La Sagra in Spain, but because it got a low NEO rating by the MPCs automated procedures it never made it onto the NEO Confirmation Page. Team member Reiner Stoss alerted observers that two nights of positions had been obtained and requested further observations via the Minor Planet Mailing List (http://tech.groups.yahoo.com/group/mpml/message/22231). A set of positions obtained just before midnight on Aug 28 from Great Shefford allowed the MPC to announce the new Amor object 2009 QY33 the next day.
On July 30th a fast moving 15th magnitude object found by the Catalina Sky Survey and designated as 9O0DC57 by them was put on the Minor Planet Center's NEO Confirmation page, only to be taken off again the next day with a note "was not a minor planet", normal procedure by the MPC when an artificial satellite is mistakenly picked up as a NEO.
This one though did not match any of the artificial satellites with published orbits. It has a perigee of 18,000Km and an apogee 1/3 the distance to the Moon, making it easily mistaken for a NEO during a close approach.
I followed it over a number of nights during August and on August 2nd managed to determine that it rotates every 5.6 seconds, following it from 00:29 UT into twilight at 03:16 UT. From 00:27 to 01:52 UT it showed a regular 1.5 magnitude variation, but when next picked up at 02:56 UT it was showing a very short flash superimposed on the regular variation, probably less than 1 second long and of about 0.75 magnitudes amplitude. Only about 10 minutes later this flash had increased to about 1.5 magnitudes. The lightcurve is from 495 measurements of 1 second exposures, folded using a period of 5.620 seconds, with the increasing flash marked with curves A and B between phase 0.10 and 0.35. The inset from a 60 second exposure started at 03:21:26 UT shows the object trail 250" long and captures 11 flashes and the secondary maximum can just be made out just to the right of the bright flash.
An 18th mag object moving at 18"/min at discovery and put on the NEO Confirmation page on August 22 turned out to be an very impressive amateur discovery by Noeline Teamo from the Hibiscus Observatory (F84) in Tahiti. Designated 2009 QC23 it was followed at Great Shefford for a week.
Another amateur NEO discovery was made on Aug 27th by the team at the OAM Observatory, La Sagra in Spain, but because it got a low NEO rating by the MPCs automated procedures it never made it onto the NEO Confirmation Page. Team member Reiner Stoss alerted observers that two nights of positions had been obtained and requested further observations via the Minor Planet Mailing List (http://tech.groups.yahoo.com/group/mpml/message/22231). A set of positions obtained just before midnight on Aug 28 from Great Shefford allowed the MPC to announce the new Amor object 2009 QY33 the next day.
Wednesday, 5 August 2009
2009 July notes: (216523) 2001 HY7, 2001 AA50, 2009 NL and 2009 OF
With the short UK nights combined with the summer monsoon starting in the South-West of the US
Aten (216523) 2001 HY7 was observed on three nights in early July, but poor weather prevented getting enough coverage to find an unambiguous rotation period before it had faded out of range by mid-month.
Better luck was had with 2001 AA50, observed on 6 nights between July 20 and Aug 2, which showed an amplitude of 2 magnitudes. A rotation period of just under 26 hours is looking most likely, though a few more nights are still needed to be certain.
Apollo 2009 NL was a LINEAR discovery made on July 13th and was predicted to be magnitude 17 through the rest of the month. Photometry was obtained on 11 nights from July 14-Aug 2 and at magnitude 17-18 the scatter of measurements on individual nights was up to +/- 0.5 magnitudes but even so a likely rotation period of 25.2 hours and an amplitude of about 1 magnitude was able to be derived (see preliminary lightcurve).
2009 OF was another Apollo discovered by LINEAR, this time on July 17th and was initially listed by JPL and NEODys as a virtual impactor. It was observed on four nights from July 19-25, finally being taken off the risk registers on July 26th.
Subscribe to:
Posts (Atom)