2026 SEPTEMBER 03

In this month’s issue:

1. … And we’re back
2. New Faces and Fond Farewells
3. Duplicated timestamps: rejections starting November 12, 2026
4. Going through SARC? Yes, it is worth it.
5. Sar2901: mini-moon or artificial satellite?
6. Our Monthly Chat about Comets

1. … And we’re back! 🥳

Hi Everyone,

It has been a while, and we know that some of you may have been wondering what happened to the Newsletter.

Your faithful newsletter writer was navigating the joys of immigration paperwork, which ended up taking a little longer than expected. That delayed a few things I was working on, and unfortunately both the Newsletter and the Circulars paid the price.

We are happy to report that everything is now back on track, and, more importantly, your favorite newsletter is back!

We have quite a bit to catch up on, so let’s get started.

2. New Faces and Fond Farewells

Goodbye, Peter!

At the end of June, we said goodbye to Peter Vereš, who left the MPC after almost nine years with us and returned home to Slovakia.

Peter joined the MPC in 2017, after a journey through small-body astronomy that took him from Modra Observatory in Slovakia to Pan-STARRS in Hawaiʻi and JPL in California before finally landing in Cambridge. During his years at the MPC, Peter worked on pretty much every flavor of small body you can imagine — NEOs, comets, impactors, interstellar objects — and contributed to everything from astrometry and orbit determination to survey performance, photometry, machine learning, and the enormous effort of preparing the MPC for the next generation of surveys.

Peter was also one of the most familiar faces of the MPC in the community. Many of you met him at conferences, or exchanged (many) emails and Jira tickets with him addressing problems, making suggestions, or requesting help. You also worked with him during interesting NEO events, or saw him acknowledged for one (or more) of the many things happening behind the scenes at the MPC.

After nearly a decade, it is difficult to summarize Peter’s contribution in just a few sentences, and it has been even more difficult to imagine the MPC without him. We are incredibly grateful for everything he has done for the MPC and for the small-body community, and, most importantly, for being such a wonderful colleague and friend.

Peter is now back in Slovakia, but fortunately for us he has not managed to escape small-body astronomy or planetary defense. So this is definitely a goodbye from the MPC, but not a goodbye from our community.

On a very personal note, it has been an honor and a privilege working with you and learning from you.

Thank you for everything, Peter.

Welcome, Ben!

Ben Cassese joined the MPC as an Astronomer in January 2026.

His research interests fall in the overlap between exoplanetary and planetary science; he is interested in comparing structures within our own solar system, such as moons, rings, and small bodies, with those around more distant stars. To do this he leverages Bayesian statistics, space-based observations with facilities like JWST and TESS, and high-precision numerical modeling.

Prior to joining the MPC he earned his PhD in Astronomy from Columbia University and his BS in Planetary Science and History from Caltech.

He also is interested in science policy and communication, having previously served as an intern at the National Academy of Sciences and the Media Fellow for the American Astronomical Association.

We are delighted to welcome Ben to the MPC, and we hope you’ll all have the chance to meet him and chat with him soon!

3. Duplicated timestamps: rejections starting November 12, 2026

The MPC is making its ingest validation a little stricter. Starting November 12, 2026, submissions containing tracklets with duplicated observation timestamps will be rejected at ingest.

What does this mean? Within a single tracklet, an object cannot have two different observations with exactly the same timestamp - after all, an object cannot be in two places at the same time!

Please note that simultaneous observations using different filters (fltr field in ADES) are OK.

This is not actually a new rule: tracklets containing duplicated timestamps have long been considered invalid and rejected later in the MPC processing pipeline. What is changing is where the problem is detected. Starting November 12, if even one tracklet in a submission contains duplicated timestamps, the entire submission will be rejected at ingest.

For now, these cases generate a warning in the acknowledgment email, giving submitters time to identify and correct any problems before the validation stage issues a hard error.

Why are we telling you now?

Because this happens more often than you might expect!

For manually prepared submissions, the most common cause is simply a duplicated observation. The solution is easy: remove the duplicated timestamps.

For large automated survey pipelines, things can be a little more complicated. We have found cases where two different tracklets, likely corresponding to different objects, have been associated with the same permID or provID. Because MPC groups observations using identifiers such as permID, provID, trksub, and artsat (in that order of priority), those observations can end up being interpreted as belonging to a single tracklet, resulting in duplicated timestamps.

If you operate an automated submission pipeline, please check your acknowledgment emails now for duplicate-timestamp warnings and make sure your pipeline can handle these cases before November 12.

And while we’re talking about warnings …

This is also a good opportunity to remind everyone to pay attention to the warning and error messages in MPC acknowledgment emails. A rejected submission should always include at least one error explaining the reason for the rejection. Accepted submissions may also contain warnings about data that are currently accepted but could trigger rejection in the future.

As we introduce new validation checks, our general approach will be to start them as warnings before turning them into hard errors, giving submitters time to identify and fix potential problems.

Warnings and errors are also available through the MPC Submission Status API:

And, as always, if one of our messages is a little too terse to decipher, please open a helpdesk ticket and ask us.

4. Going through SARC? Yes, it is worth it!

For those working with singletons or archival observations, we strongly encourage you to go through the SARC (Singletons and Archival Committee) review process. We know that the review can require a significant amount of work, and that successfully passing it is not necessarily easy, but we can also confirm that it is definitely worth the effort, both for you and for the broader community.

As part of the review, SARC will ask you to provide a clear scientific justification for the work and to explain how you have verified that the images you are using contain accurate timing and positional information. You will also be asked to provide a small sample of your observations in ADES format, so that the data themselves can be reviewed.

These requirements are important: archival and singleton observations can be extremely valuable, but understanding their provenance and ensuring the reliability of their timing and astrometry is essential before they can become part of the MPC archive.

We also know that preparing a submission for SARC can seem daunting, particularly the first time around. Please don’t let that discourage you! Going through SARC takes some work, but the result is a better understood and more reliable dataset for you, for the MPC, and ultimately for the entire small-body community. We strongly encourage anyone with potentially valuable archival or singleton observations to give it a try!

5. Sar2901: mini-moon or artificial satellite ?

The object with submitter-assigned trksub Sar2901 appeared on the MPC’s NEOCP with an orbit that is suggestive of either a mini-moon or an artificial object.

The broader community seems to be split as to which is the most favored, with both opinions being proffered to the MPC. Given the lack of consensus, the MPC would prefer to delay the assignment of a designation (which would indicate we believe the object to be natural) until the community is more broadly convinced that this is a natural object.

The object has faded from view and is likely to only become accessible to observation in the mid-to-late November (2026) period. If/when observations are obtained in the November/December 2026 period, it will be plausible to
determine the magnitude of any non-gravitational forces acting on the orbit, thus enabling a refined assessment about the nature of this object. Moreover, additional characterization observations are also likely to be taken
in that same period.

The current astrometric dataset is provided below. The observations have been assigned 'ITF' status in the MPC’s observational table and are publicly
available via the replicated database (see https://minorplanetcenter.net/mpcops/documentation/replicated-tables-info-general/), or via file download
from https://minorplanetcenter.net/iau/ECS/MPCAT-OBS/MPCAT-OBS.html.

We encourage the community to submit any unsubmitted astrometry that they already have (using the same 'Sar2901' trksub) and we will collect and publish everything in the ITF under that trksub.

We further encourage the community to contact us via our publicly available helpdesk at https://mpc-service.atlassian.net/servicedesk/customer/portals.

6. Our Monthly Chat About Comets ☄️

Starting with this issue, we’d like to introduce a new (hopefully regular) section of the MPC Newsletter dedicated to comets. Each month, we’ll use this space to share updates, highlight interesting cases, discuss changes or challenges related to comet observations and processing, and talk about topics that may be useful to the comet community. We hope this can become an informal and useful way to keep the conversation going, share what we are working on at the MPC, and hear from all of you. So, welcome to Our Monthly Chat About Comets!

Comet Identifications and Comet Numbering

Historically, the MPC’s Observations and Orbits of Comets data product has not included identifications linking comets or minor planets to numbered comets, nor identifications between unnumbered comets. In addition, when a previously known comet is recovered, the MPC has traditionally assigned a new provisional designation, with the identification of the different apparitions subsequently published (see for example MPEC 2026-F198) and, when appropriate, a permanent comet number assigned in a later circular.

These procedures reflect the historical evolution of comet discovery, recovery, and publication. While preserving the historical record remains important, MPC procedures must also evolve to accommodate the rapidly changing landscape of Solar System observations. With the beginning of the Legacy Survey of Space and Time (LSST) at the Vera C. Rubin Observatory and the forthcoming NEO Surveyor mission, the volume and cadence of Solar System observations are entering an unprecedented regime.

The MPC has already introduced a number of changes to its systems and procedures in preparation for this new era. The changes described below represent another step in that process.

Beginning December 7, 2026, the MPC will introduce three new sections, when applicable, in the Observations and Orbits of Comets update.

The first section will report identifications of unnumbered comets or minor planets with numbered comets. Identifications will be given one per line, using unpacked designations, for example:

510P = 2025 NX200

The second section will report identifications of unnumbered comets or minor planets with unnumbered comets, also with one identification per line, using unpacked designations, for example:

P/2026 A1 = P/2025 B2

or

P/2026 A1 = 2014 NW20

The third section will report newly created dual status objects, for example:

(875163) = 520P

At the same time, beginning December 7, 2026, the MPC will discontinue the practice of assigning a new provisional designation when a previously known comet is recovered.

Recovery MPECs will continue to be issued as usual, but they will identify the object as a recovery of the previously designated comet rather than assigning an additional designation for the new apparition. When the orbit is sufficiently well determined and the object meets the requirements for permanent numbering, the comet will be numbered through the usual circular process.

These changes apply prospectively and do not alter the historical record. Existing comet designations, identifications, and numbering information will remain unchanged and will continue to be maintained by the MPC. Previously assigned designations will not be removed or retrospectively modified as a result of this change.

These changes are intended to more rapidly provide a direct and consistent representation of the identity of recovered comets, while ensuring that MPC products and procedures remain scalable and useful as the volume of Solar System observations increases substantially in the coming years.

A New Fragment of Comet C/2023 R1 (PANSTARRS)

A fragment of Comet C/2023 R1 (PANSTARRS), now designated C/2023 R1-B, was identified in August 2026, after multiple observers reported a secondary condensation near the main body. The MPC received measurements from four observing teams, with observations spanning August 7–27, 2026. The fragment was announced on August 13, 2026 in MPEC 2026-P120: COMET C/2023 R1-B.

Based on subsequent discussions with observers through Jira, it appears that the secondary condensation may have been detectable earlier than initially reported. By August 12, the secondary was approximately 10 arcseconds from the primary. If you have additional astrometry of this comet fragment, particularly observations from earlier dates, we encourage you to submit them to the MPC using the packed or unpacked (if you use ADES) provisional designation (e.g. CK23R01b or C/2023 R1-B).

Observing a new comet fragment? This is how you should submit your observations.

If you observe a new fragment of a comet that has not yet been designated by the MPC, you do not need to wait for an official designation before submitting your astrometry. You can submit the observations using the fragment designation you expect it to receive. For example, if you identify another fragment of C/2023 R1, you can submit the observations as CK23R01c or C/2023 R1-C, if you use ADES.

When possible, we also ask that you open a Jira ticket in the Comets HELP section and let us know the dates on which you observed the fragment. Images are very welcome as attachments and can be particularly helpful when we are trying to associate fragment observations reported independently by multiple observers.

If you would like a description of the observed activity to be included in the discovery MPEC, you can also submit an activity report following the same procedure used for a newly discovered comet. Reports received before the fragment MPEC is issued can then be compiled and included in the discovery MPEC.

Fragment observations can be challenging to identify and connect, so information from observers—including images, descriptions, and measurements from earlier dates—can make a significant difference.

If you have any questions, please contact the MPC.