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Format for Astrometric Observations of Comets, Minor Planets and Natural Satellites

This page describes the MPC1992 80-column record format for submitting astrometric observations of comets, minor planets and natural satellites for publication in the Minor Planet Circulars (MPCs), Minor Planet Electronic Circulars (MPECs) and IAU Circulars.

Observation Types

Observations formatted according to the schemes detailed above must be sent via e-mail to obs@cfa.harvard.edu. Observations must be sent unencoded as plain text. In particular, users of MIME-compliant mailers are asked not to use BinHex/Base64 encoding! Encoded messages are not decoded by the automated processing routines (a deliberate design decision), so any encoded observation batches will not be recognized as containing observations and will be deleted.

Optical Observations

Summary of Format

Please note that TABs must NOT be used. Columns marked as 'blank' must contain spaces (ASCII 32). The Fortran formats listed below are for writing purposes.

Minor Planets (Columns 1-13)

   Columns     Format   Use
    1 -  5       A5     Packed minor planet number
    6 - 12       A7     Packed provisional designation, or a temporary designation
   13            A1     Discovery asterisk

Minor planet numbers and provisional designations are official designations assigned by the Minor Planet Center. Temporary designations are designations, preferably no more than six (6) characters long (the absolute maximum is seven (7) characters), assigned by the observer for new or unidentified objects. Temporary designations must consist of alphanumeric characters only; do not include spaces. All observations of the same "new" object reported in the same message must have the same temporary designation.

Comets

   Columns     Format   Use
    1 -  4       I4     Periodic comet number
    5            A1     Letter indicating type of orbit
    6 - 12       A7     Provisional or temporary designation
   13            X      Not used, must be blank

Periodic comet numbers and provisional designations are official designations assigned by, respectively, the Minor Planet Center and Central Bureau for Astronomical Telegrams. Temporary designations are designations, up to six (6) characters long, assigned by the observer for new or unidentified objects. In practice, temporary designations on comet observations will be very rare.

Natural Satellites

   Columns     Format   Use
    1            A1     Planet identifier [Only if numbered]
    2 -  4       I3     Satellite number  [Only if numbered]
    5            A1     "S"
    6 - 12       A7     Provisional or temporary designation [Only if not numbered]
   13            X      Not used, must be blank

Minor Planets, Comets and Natural Satellites (Columns 14-80)

   Columns     Format   Use
   14            A1     Note 1
   15            A1     Note 2
   16 - 32              Date of observation
   33 - 44              Observed RA (J2000.0)
   45 - 56              Observed Decl. (J2000.0)
   57 - 65       9X     Must be blank
   66 - 71    F5.2,A1   Observed magnitude and band
                           (or nuclear/total flag for comets)
   72 - 77       X      Must be blank
   78 - 80       A3     Observatory code

Detailed Notes

Minor Planets

Number

Columns 1-5 contain a zero-padded, right-justified number -- e.g., an observation of (1) would be given as 00001, an observation of (3202) would be 03202. If there is no number, these columns must be blank. Six-digit numbers are to be stored in packed form (A0000 == 100000), in order to be consistent with the format specified earlier in this document.

Provisional/Temporary Designation

Columns 6-12 contain the provisional designation or the temporary designation. The provisional designation is stored in a 7-character packed form.

Note

Temporary designations are designations assigned by the observer for new or unidentified objects. Such designations must begin in column 6, should not exceed 6 characters in length, and should start with one or more letters.

It is important that every observation has a designation and that the same designation is used for all observations of the same object.

Discovery Asterisk

Discovery observations for new (or unidentified) objects should contain * in column 13. Only one asterisked observation per object is expected. Some objects consist of multiple designations; in that case each designation keeps its original discovery asterisk.

Comets

Periodic Comet Number

Periodic comets that have been observed at more than one return are assigned numbers. Reference should be made to the editorial notices on MPC 23803-23804 and 24421 for more complete details of the circumstances under which numbers are assigned.

Examples:

      Comet                  P/ Number    Columns 1-4
                                          will contain
      P/Halley                  1P          0001
      P/Encke                   2P          0002
      P/Biela                   3D          0003
      P/Wild 4                116P          0116
   ```
See the complete list of [periodic comet numbers](https://minorplanetcenter.net/iau/lists/PeriodicCodes.html).


#### Orbit Type
Column 5 contains `C` for a long-period comet, `P` for a short-period
comet, `D` for a 'defunct' comet, `X` for an uncertain comet, `I` for an interstellar object, or `A` for a
minor planet given a cometary designation or objects suspected to be comets.

#### Provisional Designation
Columns 6-12 contain a packed version of the provisional designation.
The first two digits of the year are packed into a single character
in column 6 (where `I == 18`, `J == 19`, `K == 20`). Columns 7-8 contain the last
two digits of the year. Column 9 contains the half-month letter.
Columns 10-11 contain the order within the half-month. Column 12 will
be normally be `0`, except for split comets, when the fragment designation
is stored there as a lower-case letter.

Examples:
1995 A1 = J95A010 1994 P1-B = J94P01b refers to fragment B of 1994 P1 1994 P1 = J94P010 refers to the whole comet 1994 P1 ```

Columns 6-12 may contain a minor planet provisional designation. In such situations, column 12 will contain a capital letter.

Natural Satellites

Planet Identifier

A single character to represent the planet that the satellite belongs to.

Examples:

   Char   Planet
     J    Jupiter
     S    Saturn
     U    Uranus
     N    Neptune

This is given in column 1 for numbered natural satellites such as Jupiter 1, and column 9 for those with only provisional designations, such as S/2022 J 1.

Satellite Number

For those objects with Roman numeral designations, columns 2-4 contain the number of the satellite.

Column 5

Column 5 is always S for a satellite observation.

Provisional Designation

Columns 6-12 contain a packed version of the provisional designation for those objects without Roman numeral designations.

Note

The first two digits of the year are packed into a single character in column 6 (I = 18, J = 19, K = 20). Columns 7-8 contain the last two digits of the year. Columns 10-11 contain the order within the year. Column 12 will be always be 0. This is similar to the scheme used for comets.

Examples:

   123456789012
   J013S         Jupiter XIII
   N002S         Neptune II
       SJ99U030  S/1999 U 3    (Third new Uranian satellite discovered in 1999)
       SK20J010  S/2020 J 1    (First new Jovian satellite discovered in 2020)

Comets, Minor Planets and Natural Satellites

Note 1

This column contains an alphabetical publishable note or (for those sites that use program codes) an alphanumeric or non-alphanumeric character program code. The list of standard codes used for observations of minor planets is given in each batch of MPCs.

Note 2

This column serves two purposes. For those observations which have been converted to the J2000.0 system by rotating B1950.0 coordinates, this column contains A, to indicate that the value has been adjusted. For those observations reduced in the J2000.0 system this column is used to indicate how the observation was made. The following codes will be used:

```
  P   Photographic
  e   Encoder
  C   CCD
  B   CMOS
  T   Meridian or transit circle
  M   Micrometer
 V/v  "Roving Observer" observation
 R/r  Radar observation
 S/s  Satellite observation
  c   Corrected-without-republication CCD observation [MUST NOT be used on submissions]
  E   Occultation-derived observations
  O   Offset observations (used only for observations of natural satellites)
  H   Hipparcos geocentric observations
  N   Normal place
  n   Mini-normal place derived from averaging observations from video frames

  D   CCD observation converted from original XML-formatted submission [MUST NOT be used on submissions]
  Z   Photographic observation converted from original XML-formatted submission [MUST NOT be used on submissions]
 W/w  "Roving observer" observation converted from original XML-formatted submission [MUST NOT be used on submissions]
 Q/q  Radar observation converted from original XML-formatted submission [MUST NOT be used on submissions]
 T/t  Satellite observation converted from original XML-formatted submission [MUST NOT be used on submissions]
```

In addition, there are `X` and `x` which are used only for already-filed observations.
`X` was given originally only to discovery observations that were approximate or
semi-accurate and that had accurate measures corresponding to the time

of discovery; this has been extended to other replaced discovery observations. Observations marked X/x are to be suppressed in residual blocks. They are retained so that there exists an original record of a discovery. These codes MUST NOT be used on observation submissions.

Date of Observation

Columns 16-32 contain the date and UTC time, usually corresponding to the mid-point of observation. If the astrometry refers to one end of a trailed image, then the time of observation should be either the start time of the exposure or the finish time of the exposure, depending on which end of the trail was measured. The format is YYYY MM DD.dddddd, with the decimal day of observation normally being given to a precision of 0.00001 days. Where such precision is justified, there is the option of recording times to 0.000001 days.

Observed RA (J2000.0)

Columns 33-44 contain the observed J2000.0 right ascension. The format is HH MM SS.ddd, with the seconds of R.A. normally being given to a precision of 0.01s. There is the option of recording the right ascension to 0.001s, where such precision is justified.

Observed Decl (J2000.0)

Columns 45-56 contain the observed J2000.0 declination. The format is sDD MM SS.dd (with s being the sign), with the seconds of Decl. normally being given to a precision of 0.1". There is the option of recording the declination to 0".01, where such precision is justified.

Observed Magnitude and Band

The observed magnitude (normally to a precision of 0.1 mag.) and the band in which the measurement was made. The observed magnitude can be given to 0.01 mag., where such precision is justified. The default magnitude scale is photographic, although magnitudes may be given in V- or R-band, for example. In the past for comets, the magnitude was specified as being nuclear, N, or total, T, but observers are now encouraged to provide the actual band used.

The current list of acceptable magnitude bands is `B, V, R, I, J, W, U, C, L, H, K, Y, G, g, r, i, w, y, z, o, c, v, u`. Non-recognized
magnitude bands will
cause observations to be rejected. Addition of new recognised bands
requires knowledge of a standard correction to convert a magnitude in that
band to V. Conversion to V band used by MPC is located [here](https://minorplanetcenter.net/iau/info/BandConversion.txt).

The formerly-used "C" band to indicate "clear" or "no filter"
is no longer valid for newly-submitted observations, but will remain on
previously-submitted observations.

For programmatic access to magnitude bands, see the Magnitude Bands API.

Observatory Code

Observatory codes are stored in columns 78-80. Lists of observatory codes are published from time to time in the MPCs. Note that new observatory codes are assigned only upon receipt of acceptable astrometric observations per the MPC's requirements.