WELCOME BACK, HERMES 
 ================== 
 2003 October 17 
 John Pazmino 
 NYSkies
 john.pazmino@moondog.com 
[I cobbled this article from several diverse sources, so the writing 
style is uneven.] 
    After eluding astronomers for 66 years, the long-lost asteroid Hermes 
has finally been retrieved.
    Early on 2003 October 15, Brian Skiff, Lowell Observatory Near-Earth 
Object Search (LONEOS), sent measurements of four CCD images obtained 
with the 58cm Catalina Schmidt telescope to the Minor Planet Center 
in Cambridge, Massachusetts. At the Center, Timothy Spahr identified 
the suspect with other measurements submitted in the past seven weeks -- 
but not recognized as unusual -- by LONEOS and by the Lincoln Near 
Earth Asteroid Research (LINEAR) project. In addition, quick action by 
James Young, Table Mountain Observatory, secured a confirmation just 
before dawn on the 15th. 
    A bright near-earth-object candidate, reported this morning by B. 
Skiff, was placed on The NEO Confirmation Page by T B Spahr quickly 
enough that follow-up observations could be made by J Young within 
four hours. Spahr then located the Oct 5 observations (which had been 
reported as a likely main-belt object) and recognized the object as 
1937-UB (Hermes). With the help of the LINEAR Team, single-night 
observations (also reported as likely main-belt objects) could then be 
identified back to Aug 26. The initial orbital elements, omitted here, 
have not been linked to the 1937 observations, since when the object 
has made almost exactly 31 revolutions. Radar observations at the 
present apparition would be very useful. 
    Judging by its brightness, Hermes is a minor planet about 1 to 2 
kilometers across. So it could be somewhat larger than the 1937 
estimates. In a famous exhibit at the American Museum of Natural 
History, New York, Hermes was depicted as a sphere about the size of 
Central Park. 
    Hermes is by far the most famous of "lost asteroids". It was 
discovered by Karl Reinmuth at Heidelberg, Germany, on 28 October 
1937 and tracked for only five days. Although never officially 
numbered, it has been known by the name Hermes or catalog number 1937-
UB ever since. 
    In late October 2003, Hermes will be bright enough (magnitude 13) 
to be seen in 20cm and larger amateur telescopes as it races westward 
across Cetus, Pisces, and Aquarius. By month's end it will be moving 7 
degrees per day and gaining. Unlike the situation in 1937, when Hermes 
skimmed to within 800,000 km of our planet (two Earth-Moon distances), 
it will pass about nine times that far on 4 November 2003. 
Nevertheless, the possibility of future close encounters definitely 
puts this object in the Potentially Hazardous Asteroid class. 
    The discovery was announced on Minor Planet Electronic Circular 
2003-T74, issued 2003 October 15, with the inital observations from 
LINEAR and LONEOS:  
 Observations of 1937-UB (Hermes) 
 Object   -----UT Date-----  RA------(2000)------dec  Magn  Obs 
 J37U00B  C2003 08 26.35985  01 52 54.33 +04 08 41.6  18.8  704 
 J37U00B  C2003 08 26.37269  01 52 54.87 +04 08 44.8  19.6  704 
 J37U00B  C2003 08 26.38603  01 52 55.52 +04 08 46.6  19.3  704 
 J37U00B  C2003 08 26.41142  01 52 56.62 +04 08 52.1  19.2  704 
 J37U00B  C2003 09 03.37679  01 58 49.08 +04 23 54.8  19.0  704 
 J37U00B  C2003 09 03.38860  01 58 49.59 +04 23 55.5  19.1  704 
 J37U00B  C2003 09 03.40035  01 58 49.96 +04 23 55.8  18.6  704 
 J37U00B  C2003 09 03.41219  01 58 50.36 +04 23 57.0  19.3  704 
 J37U00B  C2003 09 28.29353  02 05 19.55 +04 12 35.4  16.9  704 
 J37U00B  C2003 09 28.30707  02 05 19.22 +04 12 32.1  18.5  704 
 J37U00B  C2003 09 28.31989  02 05 18.78 +04 12 30.5  18.0  704 
 J37U00B  C2003 09 28.34613  02 05 18.17 +04 12 26.7  17.0  704 
 J37U00B  C2003 09 28.37929  02 05 17.41 +04 12 21.0  17.1R 699 
 J37U00B  C2003 09 28.39356  02 05 17.02 +04 12 18.8        699 
 J37U00B  C2003 09 28.40779  02 05 16.65 +04 12 15.9        699         
 J37U00B  C2003 09 28.42207  02 05 16.31 +04 12 14.2        699 
 J37U00B  C2003 10 05.59036  02 01 02.22 +03 46 56.7  16.7  608 
 J37U00B  C2003 10 05.60121  02 01 01.55 +03 46 53.9  16.8  608 
 J37U00B  C2003 10 05.61168  02 01 00.90 +03 46 50.5  16.8  608 
 J37U00B  C2003 10 15.30771  01 45 29.04 +02 45 15.7  14.4R 699 
 J37U00B  C2003 10 15.32432  01 45 26.23 +02 45 06.8        699 
 J37U00B  C2003 10 15.34094  01 45 23.44 +02 44 57.8        699 
 J37U00B  C2003 10 15.35751  01 45 20.63 +02 44 48.9        699 
 J37U00B  C2003 10 15.51076  01 44 55.17 +02 43 26.6  14.5R 673 
 J37U00B  C2003 10 15.51215  01 44 54.94 +02 43 25.8        673 
 J37U00B  C2003 10 15.51354  01 44 54.72 +02 43 24.9        673 
 J37U00B  C2003 10 15.51516  01 44 54.47 +02 43 24.2        673 
 J37U00B  C2003 10 15.51725  01 44 54.14 +02 43 23.1        673 
 Obs  Details: 
 608  Haleakala-NEAT/MSSS. R Bambery, E Helin, S Pravdo, M Hicks, 
      K Lawrence, P Kervin, J Africano, R Maeda. 1.2-m reflector + 
      CCD. 
 673  Table Mountain Observatory, Wrightwood. J Young. 0.6-m 
      reflector + CCD. 
 699  Lowell Observatory-LONEOS. M E Van Ness, B A Skiff. 0.59-m 
      LONEOS Schmidt + CCD. 
 704  Lincoln Laboratory ETS, New Mexico. M Blythe, F Shelly, 
      M Bezpalko, R Huber, L Manguso, D Torres, R Kracke, M McCleary, 
      H Stange, S Adams, T Brothers, S Partridge. Measurers J Stuart, 
      R Sayer, J Evans, J Kommers, P Hopman. 1.0-m f/2.15 reflector + 
      CCD. 
    The orbit for Hermes was dynamically linked from 1937 to 2003 by 
Steven Chesley and Paul Chodas, Jet Propulsion Laboratory, and issued 
2003 October 16. Using sophisticated orbit determination tools, the 
difficult problem of finding a precise orbit for the long-lost and 
recently rediscovered asteroid Hermes has been solved. 
    The recovery of Hermes was announced on 15 October 2003 by the 
Minor Planet Center in Cambridge, Massachusetts. The object was 
initially noted by Brian Skiff of the LONEOS asteroid search program 
at the Lowell Observatory in Arizona, and key follow-up measurements 
were provided by James Young of JPL Table Mountain Observatory in 
California. Tim Spahr of the MPC located prediscovery observations 
from the last 7 weeks and computed the new object's orbit. Noticing 
that the orbit was very similar to that of Hermes, last seen during 
its close approach in 1937, Spahr concluded that the new object was 
almost certainly Hermes. Definitive proof of the object's identity was 
still lacking, however, because an orbit linking the known positions 
in 1937 to those in 2003 could not be found. 
    Finding the precise orbit of Hermes is difficult because its 
trajectory is very chaotic. In the 66 years since it was last seen, 
the asteroid has made numerous close approaches to both the Earth and 
Venus. Since the orbital changes at each approach depend highly on the 
circumstances of the encounter, finding an orbit with the precise 
sequence of encounter conditions that links positions in 2003 to those 
in 1937 is a challenging problem in orbit determination. 
    We have now solved this problem by using the JPL Sentry impact 
monitoring software in a novel way. Starting from the 2003 positions, 
Sentry found twelve distinct dynamical pathways that produced 
encounters in 1937, each with a different sequence of intervening 
close approach circumstances. Comparing thes e predicted 1937 
encounters with the one determined directly from the 1937 
observations, we were able to identify the most consistent candidate, 
and then zero in on the precise orbit that best matches the positions 
in both 1937 and 2003. We now know that since it was last seen, Hermes 
has made eight close approaches to the Earth and Venus to within 0.06 
AU, including an Earth approac h to within about 1.6 lunar distances 
in 1942. The new orbit solution allows us to predict future close 
approaches with great accuracy; we can now predict that Hermes will 
not approach the Earth any closer than about 0.02 AU (8 lunar 
distances) within the next hundred years. 
    The orbital elements and ephemeris below have been adapted from 
Minor Planet Electronic Circular 2003-U04, issued 2003 October 16. 
 Orbital elements by Chesley and Chodas for 1937-UB (Hermes) 
 Epoch 2003 Dec 27.0 TT = JDT 2453000.5 
 MAn 1.79511              (2000.0) 
 MDM 0.46297069     ArgP  92.39489 
 SMA 1.6548821      AscN  34.51690 
 Exc 0.6241613      Incl   6.06802 
 Per 2.13 yr    H 17.5    G 0.15    U 2 
 Ephemeris for 1937-UB (Hermes) at 0h TT 
 2003    RA---(2000)---Dec   EH-AU   SH-AU   Elong    PAng   Magn 
 10 08   01 58.54 +03 35.4   0.287   1.277   163.4    12.9   16.1 
 10 09   01 57.29 +03 30.0   0.275   1.267   164.6    12.1   15.9 
 10 10   01 55.90 +03 24.3   0.264   1.256   165.7    11.3   15.8 
 10 11   01 54.35 +03 18.1   0.253   1.246   166.9    10.5   15.7 
 10 12   01 52.63 +03 11.4   0.242   1.236   168.0     9.7   15.5 
 10 13   01 50.73 +03 04.3   0.231   1.226   169.1     8.8   15.4 
 10 14   01 48.61 +02 56.6   0.221   1.216   170.2     8.0   15.2 
 10 15   01 46.26 +02 48.3   0.210   1.205   171.2     7.3   15.0 
 10 16   01 43.64 +02 39.3   0.200   1.195   172.0     6.7   14.9 
 10 17   01 40.72 +02 29.6   0.189   1.185   172.5     6.3   14.7 
 10 18   01 37.45 +02 18.9   0.179   1.174   172.7     6.2   14.6 
 10 19   01 33.78 +02 07.2   0.169   1.164   172.4     6.5   14.5 
 10 20   01 29.64 +01 54.2   0.159   1.153   171.6     7.2   14.3 
 10 21   01 24.96 +01 39.8   0.149   1.143   170.4     8.4   14.2 
 10 22   01 19.63 +01 23.7   0.139   1.132   168.7     9.9   14.1 
 10 23   01 13.53 +01 05.6   0.130   1.122   166.7    11.7   14.0 
 10 24   01 06.49 +00 45.0   0.120   1.111   164.4    13.9   13.9 
 10 25   00 58.31 +00 21.4   0.111   1.101   161.7    16.5   13.8 
 10 26   00 48.73 -00 05.8   0.102   1.090   158.5    19.5   13.7 
 10 27   00 37.38 -00 37.7   0.094   1.079   154.9    23.0   13.6 
 10 28   00 23.83 -01 15.1   0.085   1.069   150.7    27.1   13.5 
 10 29   00 07.47 -01 59.5   0.077   1.058   145.7    31.9   13.4 
 10 30   23 47.56 -02 52.2   0.070   1.048   139.9    37.7   13.3 
 10 31   23 23.19 -03 54.3   0.063   1.037   132.9    44.5   13.3 
 11 01   22 53.42 -05 05.9   0.057   1.026   124.6    52.8   13.3 
 11 02   22 17.57 -06 24.6   0.052   1.015   114.8    62.5   13.4 
 11 03   21 35.82 -07 43.6   0.049   1.005   103.5    73.7   13.6 
 11 04   20 49.83 -08 52.4   0.048   0.994    91.3    85.9   13.9 
 11 05   20 02.86 -09 40.6   0.048   0.983    78.9    98.3   14.4 
 11 06   19 18.55 -10 04.2   0.051   0.973    67.2   110.0   15.1 
 11 07   18 39.48 -10 06.9   0.055   0.962    56.8   120.4   16.0 
    In the table Hermes's distance from the Earth (EH-AU) and Sun (SH-
AU) is in astronomical units. Its elongation angle from the Sun 
(Elong), angle of Hermes from the Earth as seen from the Sun (PAng) 
are in degees. The visual magnitude (Magn) is based on assumed size 
and albedo of hermes. 
    The orbit above is based on a computation linking the 1937 and 
2003 observations by S R Chesley and P W Chodas of NASA NEO Program 
Office at the Jet Propulsion Laboratory. They note that the trajectory 
of 1937-UB is very chaotic due to frequent and close planetary 
encounters. Between the 1937 October encounter at 0.00495 AU and the 
present encounter, 1937-UB made eight intervening close approaches to 
the Earth or Venus at distances less than 0.06 AU, including an 
approach to within 0.0043 AU of Earth on 1942 April 26.7.  
    These perturbations dramatically narrowed the region of 
convergence for differential corrections, so that very precise initial 
conditions were required to permit a least-squares fit. With the use 
of just the 2003 astrometry the JPL Sentry impact monitoring software 
(which was specifically developed to cope with such extreme 
nonlinearity) identified twelve dynamically distinct routes from 2003 
to the 1937 encounter. Comparing target plane projections of these 
possibilities with that of the observed 1937 encounter enabled them to 
derive suitable initial conditions permitting a general orbital 
solution using all data, with appropriate weighting of the low-quality 
1937 data.