A Day in the Life of the MPC

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A Day in the Life of the MPC

• Tim Spahr
• CfA/NASA/etc

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Rough Outline

• 1) Background, mission, and goals
• 2) Near-earth Objects
• 3) Everything else!
• 4) What the MPC does
• 5) Semi-detailed daily timeline including
  processing steps, fun stuff, etc

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Background and charter

• The Minor Planet Center (MPC) is responsible for
  the designation of small solar system bodies
  comets, minor planets, and natural satellites, as
  well as keeping track of their orbits and
  locations.
• HUGE job on staff of 4
• Total obs database 33 million lines
• Total orbit database 300,000 objects

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Defining the orbit

• --use orbital elements two shape parameters
  (semi-major axis, eccentricity)
• --angular orientation parameters (inclination,
  longitude of nodes, etc)
• --orbit in space requires 6 (!!) constants to
  describe the motion
• --because we only see 2-d projections (the sky)
  this can get messy, confusing, and degenerate.
  Yikes!

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Near-earth Objects

• --NEOs scare people so we try to do something
  about it
• --NASA funding several surveys to scan the sky
  for the most dangerous objects
• --how do we find them?
• --bit brief since youll have a talk by someone
  else on this subject later

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What the MPC does

• -- Identifies objects submitted by surveys
• --compute improve orbital elements
• --Both of these tasks can be REALLY messy!
• --Ids take lots of computing
• --orbit refinement includes 6-dimensional
  differential correction planetary
  perturbations. Lots of math

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MPC work contd

• --scan for possible new NEOs in all that data
• --several program for computing chance that an
  object is a new NEO
• --post these objects on the web to faciliate
  additional observations
• --refine the orbit and announce the object

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Amateur connection

• --significant fraction of work done by unpaid,
  yet very skilled, amateur astronomers
• --amateurs still discover comets (and make money
  at it!)
• --lots of NEO follow-up from amateurs
• --2.5 of new discoveries from amateurs
• --unfortunately amateur contribution dropping off
  as more money aids effort

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Orbit Determination

• --MPC uses several methods for orbit
  determination
• --Gausss method (time-honored standard over 200
  years old)
• --Vaisala method (perihelic fits)
• --Marsdens method (placing object not at
  perihelion)
• --all methods then fed to differential correction
  routines

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Differential correction

• --messiest part of the whole business
• --adjustment in 6 dimensions
• --requires summation of all forces on the object,
  most importantly those perturbing forces of the
  other planets and largest asteroids
• -- does adjustment based on minimizing the error
  in the sky positions!

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Identification methods

• -- identification of survey unknowns is
  computationally intensive and involves several
  steps
• -- fill grid of the entire sky with expected
  positions of known objects
• -- compare position and rate of unknowns with
  grid positions
• -- if you get a possible match, improve the orbit
  and check residuals

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Identification contd

• -- other methods adjust position in the orbit
  based on small shift in observation time
• -- brute force method simply comparing all
  possible combinations of objects/orbits (this
  step often requires a few million calculations!)
• --similarity check are 6 orbital elements
  similar to anything else in the files?

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Identification, again!

• --CRYPTO-SUPER SECRET METHODS!
• --each MPC staffer has developed their own method
  for finding the occasional odd identification or
  linking the occasional recalcitrant case
• --these involve assumed elements, complete guess
  work, fudging orbits, and basically anything else
  you can or cannot think of
• --remember the process is iterative. If youve
  not right, keep cranking and you might get lucky

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Finally--- the timeline

• Midnight EST on a typical day
• --NEO obs arrive during the night from various
  surveys around the world. After all, it is
  always night somewhere.
• --6 AM, I usually log in to find out if we were
  plunked by space rocks, or will be plunked by
  space rocks, in the next day - )
• --after brief check, drive to the office

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Timeline contd

• --7 10 AM NEO obs arrive from big surveys in
  Arizona Spacewatch and Catalina, and perhaps
  LONEOS
• -- often 100 potential NEOs
• -- additional obs of main-belt objects arrive
• --often 10-50 THOUSAND observations
• --10-11 AM announce new NEOs with good orbits

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Timeline contd

• -- noon eat lunch, relax, and get psyched up
  for the next deluge. It is coming!
• -- 1 3 PM obs from NEAT/JPL arrive
• -- often another few dozen potential NEOs
• -- then another 25,000 obs of MBAs
• -- 4-6 PM, the big batch from LINEAR arrives
• --often 100 potential NEOs and 10,000 MBAs

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Timeline contd

• --nope, not done yet. After posting potential
  NEOs from surveys, by 6 PM it is dark in Europe
  and follow-up observations arrive
• -- 6 PM - ? Update NEOCP and sleep
• --start the whole thing all over again the next
  day

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Unusual stuff

• -- the previous day didnt include anything odd,
  like the discovery of a new planet, or a very
  close-approaching asteroid
• --anything special requires special attention and
  may take away the staff from the routine work
• --folks often upset if we are not responding to
  them with the usual speed!
• --often long hours and long days when there are
  new and exciting/unusual objects found

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General Summary

• --MPC handles observations of new objects and
  designates them. Computes orbits and
  disseminates information
• --Effort clearly needs to be expanded and
  automated, but for the moment things work
• --MPCs main role is in support of NASAs NEO
  effort
• --MPC folks handle a lot of different stuff

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And finally

• --as my favorite high school teacher used to say
  Questions, comments, or reactions?