Guide to Minor Body AstrometryThis guide is intended for those observers interested in observing minor planets, comets or natural satellites of planets, and reporting those observations to the Minor Planet Center.
Please use Jira for any questions or feedback.
How do I begin?
- What equipment do I need?
- What sort of CCD should I use?
- How do I make measurements?
- Where should I obtain my comparison star coordinates?
- What corrections should I apply to the derived positions?
- How do I obtain an accurate time?
- What objects should I be observing?
How do I report observations to the MPC?The observation format requires an observatory code. If don't have it, you should apply for one.
- How do I get the observatory code?
- Does my observatory code move with me?
- Are there any restrictions on my observatory's name?
- How do I begin?
- How do I report my astrometry?
- What's the ADES format?
- How many observations should I make of each object?
- What quality of measurements should I aim to produce?
- Can I report approximate or preliminary measures?
- Do I need to identify objects?
- Should I separate my comet and minor-planet observations when submitting them?
- What about batches containing observations from two or more observatory codes?
- Are there any recommendations regarding e-mail?
- What if I use spam-blocking systems?
- How do I know that the Minor Planet Center has received my observations?
- A message to the MPC bounced. Do I need to resend it?
- What is the purpose of the contact details?
- What are some common mistakes?
How many nights should I report?
- What about coverage on a single night?
- What is the difference between reporting two-nighter and single-nighter new objects?
- What if I can't follow-up a new discovery?
What about new discoveries, discovery credits and naming?
- When should I use a discovery asterisk?
- I think I have something new. How do I get a provisional designation assigned to it?
- Who gets credit when single nighters are linked?
- What's the best way to get my discovery numbered?
- When can I name my discovery?
- What happens to accepted observations?
- What objects go on to the NEO Confirmation Page (NEOCP)?
- How do I understand the designations the MPC sends me?
- How quickly are observations processed by the MPC?
- What (p)recovered objects get MPECs?
You must not attempt to derive positions by overlaying charts on your images or by estimating positions by eye. The accuracy of these positions will not be sufficient.
The MPC also encourages submitters, especially those searching through archival astrometry, to carefully examine any marginal detections. Astrometry should be reported only for detections with a sufficiently high signal-to-noise ratio to withstand external independent review of the images. We note that synthetic tracking software, such as Tycho Tracker, often requires significant experience to avoid submitting stacked noise in sky location of the expected position of an object.
It is the recommendation of the Minor Planet Center that observers should migrate to using the Gaia catalogues (DR2, DR3 and future ones). Other acceptable catalogues include UCAC4 and UCAC5.The following sources MUST NOT be used for comparison-star coordinates:
- The World Coordinate System information in the FITS headers for images in the Digital Sky Survey (whether accessed via the Web or via the highly-compressed CD-ROM version).
- Any B1950.0 star catalogue (e.g., SAO Catalogue).
No corrections should be made by the observer for parallax and no attempt should be made to correct the UTC times of observation to Terrestrial Time (TT), the uniform timescale used in orbit computations. the paper by Farnocchia et al (2022) containing the results of the first IAWN campaign).
Note that the determination of an accurate time for an observation depends not only on having access to a reliable standard, but also by understanding the delays in the observing system.
- The first step consists in obtaining the current UTC from the U.S. Naval Observatory's Time Service Department
- Then we suggest observers to regularly check their estimated observation times against GPS satellites. For more information about how to do it, please see the page 'Calibrating timing of astronomical images using navigation satellites' on the Project Pluto website.
Other services are also available, such as NEOfixer or the Priority List from ESA.
Some observers have set up their own web pages, generally to encourage follow-up of their own discoveries. We have collected together some of these sites, but if you wish to be added to the list, please let us know through Jira.
Ephemerides for minor planets can be generated using the Minor Planet Ephemeris Service.
"Roving Observers", for use by observers at temporary sites, applications for observatory codes are always strongly encouraged.
- New Observatory Code Request Form: please submit the form before requesting an observatory code.
- Your initial submission should contain at least six numbered minor planets each, on pairs of nearby nights as well as one numbered Near-Earth object observed on two distinct nights. If weather interferes, the two nights can be some weeks apart.
- Report at least three observations of each object from each night: do not report single positions per night.
- In your initial batch, please submit astrometry of objects fainter than 14 magnitude. Also, as a general rule, we advise not to observe very low numbered (e.g. (1), (2), ...) and very bright objects. Until the minimum amount is not submitted, MPC will not assess the submitted astrometry.
You must also report:
- A snail-mail address (used as a contact address on the observatory headers in the Minor Planet Circulars);
- An observatory name and site name;
Longitude, in degrees, minutes and seconds (not decimal degrees)
E of the Greenwich meridian, in the WGS-84 system.
To avoid any possible confusion, avoid using negative longitudes. Give a
longitude as either:
- a specific number of degrees E or W (being sure to state which direction) of the Greenwich meridian (avoid the use of negative quantities);
- a specific number of degrees E of Greenwich (according to the IAU convention). If a site is just west of the Greenwich meridian, give the longitude as a quantity near 360°, not as a negative quantity.
- Latitude, in degrees, minutes and seconds (not decimal degrees) N or S of the equator, in the WGS-84 system;
- Altitude (in meters above sea-level);
- The source for the specified coordinates (e.g., Google Earth, named map, etc.);
- Details of your telescope setup;
- Please follow the istructions reported on the how to specify observational details page
- It is also important that you specify COD XXX in the observation header for your initial batch. Do NOT use, for example, COD 000 or COD 999, as these are assigned codes and may cause your initial batch to be processed as if it contained observations from the code you used. Neither should you attempt to use a currently-unused code.
- Submit your astrometry using the format specified in 'How do I report my astrometry?'
- The longitude and latitude must be specified to an arcsecond or better. A useful tool for determining your site's coordinates is the Google Earth package: you should quote your longitude and latitude to a precision of 0".1 or better. Note that we now use Google Earth to check out the given coordinates. If we have a query as to the location, we may ask for clarification based on our description of the environment shown around the given coordinates in Google Earth.
- If you do not use Google Earth, it is important to note that the longitude and latitude that you supply must be geographic coordinates, not geocentric coordinates.
A convenient way to supply the above information in a form that is preserved
by the automated processing routines is to use the COM keyword. E.g.:
COM Long. 239 18 45 E, Lat. 33 54 11 N, Alt. 100m, Google Earth
- Astrometry with post-fit residuals larger than 2 arcseconds is going to be rejected and the observatory code will not be assigned.
- If you request an observatory code during MPC preparation time, you will experience a longer than usual delay before an observatory code is assigned. Note also that assignment of new codes is done in batches every week or so.
- If you fail to supply sufficient observations in your initial batch or fail to supply all required information, it is possible that you will experience a longer than usual delay before an observatory code is assigned.
- Even if you interested only in comets, it is required that you follow these guidelines for your initial batch and not submit comet astrometry.
If something is not clear or you don't know why your data have been rejected, please open a Jira ticket before trying to send more data to us.
No, in the sense that we cannot dictate what you choose to call your observatory.
Yes, in the sense that we don't have to use your observatory's name in the MPCs if we don't think it is appropriate. Proper names or names of living people should not be chosen as site names.
Please be careful when you select your site name.
- If your site does not have an observatory code, ask for it!
- If possible, report at least three observations of each object from each night: do not report single positions per night. As a general rule, batches that contain single positions will be returned in their entirety to the submitter.
- You should not start by observing fast-moving objects. It is important that you gain experience by observing "routine" objects before attempting to observe "unusual" objects. We also expect you to prove that you can produce good astrometry of known objects before you begin to discover new objects.
- In general, comets are harder to measure than minor planets. If we have a new observer reporting comet observations of bad or indifferent quality we do not know if it is simply a problem due to the comet (big, bright difficult-to-measure image) or a problem with the measurement/reduction process.
- The MPC encourages submitters, especially those searching through archival astrometry, to carefully examine any marginal detections. Astrometry should be reported only for detections with a sufficiently high signal-to-noise ratio to withstand external independent review of the images. We note that synthetic tracking software, such as Tycho Tracker, often requires significant experience to avoid submitting stacked noise in sky location of the expected position of an object.
- Reporting magnitudes is optional, but highly desirable. Please try to report magnitudes if you are submitting archival astrometry.
MPC encourages observers to use the correct keywords in the observational header, particularly when it
comes to rapid processing of NEOs or comets. Without the correct keyword, tracklets could end up in a
wrong or slower queue. In addition, please submit new NEOs separately from NEOCP followup and/or
incidental astrometry. Lastly, please follow the instructions on how to format other elements of the header. Issues
such as omitting space between initial and last name slows down the process of the submitted astrometry
since the automated program code assignment will not be possible (follow the istructions reported on the
how to specify observational details page).
- Batches containing observations of new NEO candidates must have "NEO CANDIDATE" in the subject line.
- Batches containing observations of objects already on the NEOCP must have "NEOCP" in the subject line.
- Batches containing observations of new comet candidates must have "NEW COMET" in the subject line.
- Batches containing observations of new TNO candidates must have "NEW TNO" in the subject line.
- See 'How do I report my astrometry?' to understand what format you need to use to report your observations.
- See also 'What quality of measurements should I aim to produce?'.
- The longstanding 80-character MPC1992 format (also informally called obs80)
- The more recent IAU Astrometric Data Exchange Standard (ADES).
Observations reported in ADES format needs to follow the rules described in the ADES documentations and on the MPC MPC ADES Data Submission page. Observations of minor planets, comets and natural satellites, formatted as specified in the link above, can be reported via:
- Do not report more than one position for each time of observations. Observations of objects that contain multiple positions for a single time of observation will be returned to the submitter for correction.
- When there is no trailing of the minor planet image (or you are measuring the middle of a trail) the time of observation is the mid-exposure time. If you are measuring both ends of a trail, then one end is associated with the start of the exposure, the other with the end. Alternatively, if the trail is very short, you can simply report the mid-point. However, you must not report both a trail-end and mid-point measures from the same trail.
- Note that reported magnitudes must be derived from the individual frames: do not obtain a magnitude from one frame and then copy it on all the other observations. Also, ensure that you report the magnitudes with the astrometry: do not say "Photometry to follow".
- Always report positions for every moving object in your images. Do not assume that just because an object is numbered that continuing observations are not important. The inclusion of well-known objects, particularly when there are also observations of unidentified objects, serves as a useful check of the quality of your measurements.
Details are available on the ADES GitHub repository and on the MPC ADES webpage.
The use of the ADES format is not mandatory at the moment, but the MPC strongly encourage users to familiarize themselves with the format and the repository.
- The MPC typically recommends taking a few observations over a period of an hour or so per object, per night. Additional astrometric positions are typically not helpful for the determination of the orbit.
- Observations of specific objects are best made on pairs of nearby nights as the accuracy of isolated single-night observations can be difficult to judge. By observing on pairs of nights any ambiguity is removed.
- Please try to not make only one observations of each object per night. Without specific appropriate reasons, if a batch contains any single positions, the entire batch will not be accepted and it will be returned to the sender.
- Observations of a potentially new object in groups many hours apart on a single night can be useful in particular in the case of a newly-discovered object that may be close to the earth.
A few additional notes:
- Please check if you have any timing errors before submitting observations (see the 'How do I obtain an accurate time?' point.)
- Please note that if you are using the ADES format, you are also able to report your astrometric uncertainties. Be sure you have read how to compute and submit your uncertainties in the ADES documentation.
Approximate measurements will be ignored. Only report final astrometry.
Don't report preliminary measures and then improve them. It is very time-consuming to replace preliminary measures.
If you do not identify the object, the MPC checking procedures will first check if the object can be linked to any known solary system objects before processing it.
However, every reported observation must have a designation. If you don't know the designation of a particular object, or are not bothering to identify objects, use an observer-assigned temporary designation. Observer-assigned temporary designations should be unique--don't call everything `X'!
Observer-assigned temporary designations should be seven characters or less long, and begin in column 6 of the observational record. The designations must not be of the form of the packed (e.g. K23A00B, 00001, ~0023) or unpacked designations (e.g. 2023AB, 1, 620127) used by the MPC. Also:
- Observations of NEOCP objects must always be tagged with their NEOCP designations. as well the initial observations made in support of an observatory code request.
- Observations reported for the first time when asking for a new observatory code need to include the provisional designation or the number that identifies the object.
- Observations of the same object on different nights must be given the same temporary designation only if they are reported in the same message and you are absolutely positive that all the nights refer to the same object. Correspondences of observer-assigned temporary and MPC-assigned provisional designations will be reported back to the observer via e-mail (see also 'How do I understand the designations the MPC sends me?')
- Do not continue to use your observer-assigned designations once official provisional or permanent designations have been assigned.
COD 608 OBS ... MEA ... ... Rest of header ... Observations from code 608 COD 644 OBS ... MEA ... ... Rest of header ... Observations from code 644Failure to format the message as shown above will result in the batch being rejected by the automated routines. Note that later headers do not inherit anything from earlier headers. So you must include, at a minimum, OBS/MEA/TEL/NET lines on later headers.
Note that this scheme must be followed if there are two (or more) headers from the same observatory code in the same message. cURL submission method to submit the observations. If you submit ADES observations, the cURL method is also the only method allowed. In case you are submitting observations in the MPC1992 format and you want to use the e-mail, the following guidelines should be noted with regard to any e-mail submission of observations:
- Observations must be reported as plain ASCII files. Do not send, e.g., UUENCODE'd or BINHEX'ed files. This is important if you are using e-mail attachements.
- Please ensure that your mailer does not split the 80-column observation records--many mailers, such as PINE, will automatically break a line at about 72 characters. In PINE you can avoid this problem if the observations you wish to send are in a separate file by including the file using CTRL-R, rather than by using cut and paste.
- If you are using a mailer that can send HTML mail, please disable the inclusion of the HTML version. Inclusion of the HTML version more than doubles the length of the e-mail and the repetition of material is completely useless. In addition, the inclusion of HTML text may trigger the MPC's antispam e-mail filters, causing your message to be flagged as spam. Information on sending plain-text e-mails from Hotmail is here.
- Never send any kind of word-processor/DTP file. If you use a word processor or DTP package to prepare your observations, ensure that you use the package's `Save as ASCII' option.
Or you can use the cURL submission method to submit batches of any size.
Note that "Allowed Sender" systems will not work with our automated routines that send out information as e-mail returned to certain addresses will bounce.
If you have not received any acknowledgement from us or if you want to know what happened to your observations, please use our WAMO service.
Please also check that you have correctly used all the fields in the header. See Information on how to personalize the acknowledgement is available.If something is not clear or you still have questions about your observations, please submit a Jira ticket.
Note that the acknowledgement is automatic and simply informs you that we have received your message. It says nothing about the formatting of the observations contained therein or their quality.
You should only resend your message if the bounceback indicates that obs@cfa is the source of the failure.
You do not need to resend your message if the bounceback comes from any other e-mail address. MPCs for each observatory code are intended as a contact point for persons with queries regarding a specific program. The contact address does not have to be the street address of the observatory. For professional programs it should be noted that the contact details are NOT intended to be a list of P.I.s on the project.
The contact details MUST include:
- the name of a person connected with the program (who is willing to answer queries about the presented observations)
- a snail-mail address for that person (this can be a P.O. Box)
- an e-mail address for that person
If you try to identify objects, ensure that the identifications are correct and that you used the packed forms of the designations in the appropriate columns of the observational records. If in doubt, use temporary designations.
Incorrect Times of Observations
Ensure that the mid-points of your exposures are timed and reported correctly! The most common error by observers (and one of the trickiest to correct if the observation has already been published) is incorrect observation times (or occasionally even dates).
Ensure that you send only plain ASCII e-mails. Encoded attachments will be ignored by the automated processing routines.
Incorrectly-Specified Observer Details.
If you do not include an observational header before the observations, the e-mail message will not be recognized as containing observations.
Some observers specify observer details in the form used in the MPCs. These details are usually nicely formatted, but the observation processing routines will ignore them. Observer details must be formatted in the proper format.
If you are stacking images, try and ensure that you produce at least two stacks, remembering that the stacks have to be independent, so an image cannot be used in more than one stack. If you can produce only one stack, ensure that the observation is marked as a stack ("K" in column 14). If you produce more than one stack, mark the observations as stacked unless there is another note you wish to use. If you are observing at a site that uses codes to distinguish between different programs, the "K" should appear on the submitted observation, but will be replaced by the program code during processing. How do I report my astrometry?).
If you have observed a new MBO on one night and you are not able to obtain a second night within a week or so, you should report the tracklet anyway.
The observations will be subject to the normal checking procedures of the Minor Planet Center (see 'Do I need to identify objects?'):
- If the object is confirmed as a new NEO, it will go on the NEO Confirmation Page and it may get follow-up for other telescopes.
- If the object is not an NEO, but it is identified with a known MBO, then the observations will be published.
- If the object is not an NEO and it cannot be identified with any known objects, then the observations are sent to the Isolated Tracklet File (ITF). ITF is regularly checked against new orbits and matches are extracted and published under the assigned designations.
If someone does follow-up for your new objects, you will get credit for the discovery even if you have obtained only one night's observations. However, there is nothing preventing your colleague from getting two nights on your new object and then reporting it to us as a new object. In such a case, credit will be given to your colleague. For this reason, you should not distribute observations of the new object and you should only send ephemerides to colleagues that you trust (see also 'Who gets credit when single nighters are linked?').
Discovery asterisks on submitted observations must only appear on observations with observer-assigned temporary designations. They must never appear on submitted observations with MPC-assigned designations.
There can be more than one discovery asterisks for objects that have not yet been numbered. The MPC will assign the final asterisk when the number and the discovery credits are assigned. See also this Editorial Note for a more extensive explanation.
The information is published in the monthly Minor Planet Circulars (MPCs)
Note that following the Editorial Note on MPEC
2010-U20 the assigmment of a new provisional designation does not mean that you will
be credited with the discovery of the object when it is numbered. The afore-mentioned
MPEC should be read to see the new rules regarding discovery credit and the
grandfathering of old multiple-opposition objects. The use of the terms "discoverer" and
"discovery" in this document are to be interpreted according to those rules.
New designations are assigned when we have enought observations to compute a reliable orbit. You may use the on-line New Object Ephemeris Generator to generate ephemerides to enable you to find the object after the first night.
Note that this linking process requires the earlier observations be on a different night (at least 12 hours separation) and to be of good quality. MPEC 2010-U20 are located.
Once identified (or recovered as a result of a direct search), observations should be made on pairs on nights in each of two dark runs at each opposition until the object is numbered. For main-belt objects this can occur after the object has been observed at four oppositions (although this depends on the number and distribution [preferably two nights in each of two dark runs in at least three of the oppositions] of the observations as well as their quality); NEOs can receive a number after two or three well-observed oppositions. In addition, objects to be numbered require the uncertainty parameter, U, must be less than or equal to two. Note that newly-identified multiple-opposition objects are not eligible for numbering: numbering of such objects can only take place after the first multiple-opposition orbit has appeared in the MPCs and after further observations have been reported (these can be at the latest opposition, or at an earlier or subsequent opposition).
The selection of objects for numbering is an automatic process performed just before the preparation of each batch of MPCs. There is no need to ask us "What do I need to do to get such-and-such numbered?". Simply follow the guidelines above and the object will be numbered when it is ready.
- Names for minor planets are proposed by the discoverer of a specific object after the object is numbered. Proposals are accompanied by a brief citation explaining the reasons for the naming.
- Names and citations proposed by discoverers are judged by the Working Group Small Body Nomenclature (WGSBN) of the International Astronomical Union. The WGSBN has published the rules and guidelines relating to the naming of minor planets, as well as the special naming rules for objects in certain orbital classes. The document also includes information on the procedures used to accept or reject proposals.
- Names become official when they appear in the WGSBN Bulletin, published by the WGSBN.
- When several provisional designations belong to the same numbered minor planet, one of these provisional designations is defined as the principal designations (this is decided when the object is first identified) and it is the discoverer of this principally-designated object that is defined as the discoverer of the numbered object.
- An alphabetical list of current minor planet names is available. A list of the discovery circumstances of the numbered minor planets is available.
If you need more information about how to write the citation and submit the name, what names are acceptable, how long it takes for the name to be approved, please contact directly WGSBN, using their contact email address email@example.com.
- Observations of NEOs are published daily in the Daily Orbit Update (DOU, e.g. see MPEC 2023-Q03). The DOU is available online from the Recent MPECs page.
- All the other observations are published in the monthly Minor Planet Circulars (MPCs) or Supplements.
- Minor Planet Electronic Circulars are published for newly discovered NEOs, TNOs and natural satellites.
- Observations and orbits of comets and A/ objects are also published (~weekly). (e.g. see MPEC 2023-P65)
As of MPEC 2023-D40 (February 21, 2023), Datacite DOIs are available for all new MPECs. The first published DOI is now available https://commons.datacite.org/doi.org/10.48377/mpec/2023-d40. NASA ADS, based here in Cambridge (MA) at the Center for Astrophysics, is in the process of mining the relevant data from Datacite, so that MPECs will be available on their system soon. This will allow all our users to cite their observations in scientific articles or proposals. The MPC is also in the process of creating DOIs for all the MPECs that have been released before February 21.NEO Confirmation Page are those objects which, on the basis of their motion or orbit, appear to be NEOs and that have a digest2 score larger than 65. Objects that are suspected of being comets also appear.
When removed from the NEOCP, the inner-solar-system objects that get put on to MPECs are as follows:
- Any object with perihelion distance less than 1.3 AU
- Any object with an perihelion distance beyond 5.5 AU (Centaurs/SDO and TNOs are not listed in only one-opposition)
- "Main-belt" objects with eccentricities above 0.5
In the past, objects with perihelia beyond 1.3 AU and eccentricities between 0.4 and 0.5 and/or inclinations above 40 degrees might appear on an MPEC if there was not much activity. This was deemed to be somewhat arbitrary (particularly in light of the fact that the major surveys were counting how many discovery MPECs they had!).
By0001 (03244 ByLa01 J99A18T ByLa02 (J81U78A By0004 (By0003 By0003 (J99A08HThis may be interpreted as follows: By0001 is the numbered object (3244); ByLa01 is a new object 1999 AT18 that is credited to Byers and Langly; ByLa02 is the known unnumbered object 1981 UA78; By0003 and By0004 refer to the same object, now designated 1999 AH8, which is a recent discovery by another team.
In short, provisional and permanent designations not prefaced with `(' are your discoveries. Provisional and permanent designations will be in the packed form, as used on the observation record.
New designations are not assigned to objects observed on only one night, although you may receive designations if such objects can be identified with already-known objects.
- Potential new NEOs/unusual objects and comets, suitable for posting on the NEO Confirmation Page.
- Follow-up observations of NEOCP objects.
- Other NEO observations.
- Survey observations from last night and recent non-survey material.
- Older non-survey material.
- Survey observations from before last night.
Note that the different processing classes are dealt with at different rates. This does not affect the order in which "new" objects are processed.
The MPC Processing times page reports the current MPC processing status for some of our pipelines with highest priorities.
Precovery refers to the identification of images of a single-apparition object at an earlier opposition.
The Recovery Page provides new unpublished observations of NEOs and TNOs that are extending the arc from one opposition to multiple-oppositions and for which additional observations are highly-desiderable. Once new observations provide at least two distinct nights on the second apparition, a recovery MPEC will be issues and the published observations will be removed from the page.
format is advisable. guide to minor planet photometry is available from Brian Warner.