Astrometry

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Astrometry involves getting precise co-ordinates of objects such as comets and minor planets (asteroids) relative to the "fixed" background stars. These observations are reported to the to the Minor Planet Center via specially formatted e-mail.

The first batch of observations submitted to MPC also consist of a request for an "observatory code". The MPC assigns a code upon receipt of acceptable observations. For more information, please see MPC's "Guide to Minor Body Astrometry".

Astronomic observations are made by taking digital images through a CCD camera, and determining the position of the minor planet or comet in relation to stars contained in the USNO-A 2.0 catalog of approximately one-half billion stars.

Astronomic data reduction (to determine positions) is accomplished through the use of the software package, Astronomica. The reductions are reported according to a special format for reporting astrometric observations to the MPC.

Prior to submitting observations to MPC, a number of prerequisites had to be completed, including telescope and CCD camera preparation, software installation and configuration, and target selection.

The test targets, which would later be used to submit astrometric observations to MPC and qualify for an observatory code, are minor planets:

(1865) Cerberus [Apollo group]
(1916) Boreas [Amor group]
(5143) Heracles [Apollo group]

The astrometric CCD-observing program began on October 9 with a review of the MPC Guide to Minor Body Astrometry. In the following weeks, minor planet targets were selected, and observational test runs and astronomic data reductions were completed on the nights of October 11-12 and 18-19 to resolve any program and system issues.

"First light" to acquire observational data to be submitted to MPC was an image containing the minor planet (1865) Cerberus on October 24 at 02:54:14 UT (start of image integration). A total of 35 observations were completed over three nights; October 23-24, 25-26, and 30-31. Below is a Astrometrica screen shot of the first light observation data reduction. In the observation image, reference stars are circled in green, and Cerberus is outlined by a small, red box.


After data reductions were completed, the first batch of observations was submitted to MPC on November 13 at 04:55:06 UT.

The MPC automated e-mail response indicated that the astrometric observation report was correctly formatted, but that 24 of the 35 observations were rejected due to "inconsistencies in the measures [astrometric observations] (as determined by their departure from great-circle motion)". Revisions to the measures were subsequently made, re-submitted, and accepted on November 13 and 14.

On Wednesday, November 19 at 4:31 PM EST, Newcastle Observatory was advised via e-mail from Gareth Williams, Associate Director of the Minor Planet Center, that it was assigned observatory code H61. This signifies that Newcastle Observatory is capable of making astrometric observations of acceptable quality.

Part of the observatory's mission will now be to gather astrometric observations of small solar system objects (minor planets or asteroids and comets) and submit those measurements to the Minor Planet Center on a regular basis. The goal is to obtain follow up observations on objects so that their orbits can be better defined.

The Minor Planet Center (MPC) operates at the Smithsonian Astrophysical Observatory (SAO), under the auspices of Division III of the International Astronomical Union (IAU). The MPC is responsible for the designation of minor bodies in the solar system: minor planets; comets, in conjunction with the Central Bureau for Astronomical Telegrams (CBAT); and natural satellites (also in conjunction with CBAT). The MPC is also responsible for the collection, computation, checking and dissemination of astrometric observations and orbits for minor planets, comets, and natural satellites. The MPC derives its current operating budget from a NASA grant.