2023 Occultations by Near-Earth Asteroids - Updated 2023 January 19
Occultations by Didymos, target of NASA's 1st planetary protection DART Mission, have the highest priority
Some important last chances to observe Didymos occultations in 2023
These occultations are described and illustrated (with maps and tables) in this .pdf document. IOTA will have campaigns for some of the early 2023 Didymos events. There are hot links to external Web pages, but links to internal files, especially the .xml input files used by the Occult program, are given below. And see at the end, links to papers and presentations about NEA occultations that give important background information. Especially for those less familiar with occultations, some good links are in the short "Basic Information" section after the Goal paragraph below. See farther down this page for maps and other UPDATED information about the good bright occultations by Didymos in January. THE GOAL On 2022 Oct. 15, the first ccultation by Didymos was observed by Roger Venable in Oklahoma, in spite of hitting a deer on his way to his observation sites. IOTA and the ACROSS project are now trying to secure additional observations. The ACROSS and JPL predictions are currently in close agreement, but more occultations by both Didymos and its battered moon, Dimorphos, are needed to better determine the orbits of both objects, to help ESA'a Hera mission that will launch in Oct. 2024 and rendezvous with the Didymos system in Dec. 2026. On 2022 Oct. 19 and Nov. 12, occultations by both Didymos and Dimorphos were recorded in Florida and southern California, respectively. We are trying to get observations of a few more occultations by Dimorphos; please help us with these efforts. By about March, the apparent motion of Didymos will increase, making the Dimorphos events too short to record with common video systems; also, Didymos will recede from Earth so far that diffraction smearing will also likely prevent observation of their occultations. Success before that will allow a more accurate determination of Dimorphos' post-DART-impact orbit than can be obtained by other means; the asteroid is already too far from Earth to be observed by currently operational radar systems. The errors of the orbit of Dimorphos, determined from rotational light-curve (transit) observations, are growing, so we hope to obtain a few Dimorphos occultation detections to reduce those errors. BASIC INFORMATION ON HOW TO RECORD OCCULTATIONS For those less familiar with recording occultations, you can learn about the main techniques, equipment, and software currently used in a good primer by George Viscome. Some more detailed information can be found in the observing tab of IOTA's main Web site. WEATHER FORECASTS Usually, we will provide little, if any, cloud cover forecast information on the event Web pages, like we did for some previous events. Mobile observers are encouraged to get their own cloud cover forecasts for their target areas, using Web sites and advice that I give on this cloud-cover forecast Web page. _ _ _ GOOGLE EARTH FILES FOR DIDYMOS OCCULTATIONS Since the paths for these events are all very narrow, one must travel to the paths with mobile equipment to observe them, rather like grazing occultations of stars by the Moon. And like lunar grazes, it is necessary to adjust the location for elevation above sea level. John Irwin in the UK has helped IOTA with this by supplying special Google Earth files that take elevation into account. Consequently, we can not use Occult Watcher (OW) for these events, since OW does not take elevation into account. Instead, we use the Google Earth (GE) files by J. Irwin that he describes in this .pdf document. Recently, Dave Herald has updated his Occult4 program to generate GE files similar to John Irwins, but Dave uses the same color scheme used in other parts of the program, so unlike Irwin, Heralds central line is green, the limits are dark blue, and the 1-sigma limits are red. The parallel fence lines for observers are light yellow and can be set up with a specified spacing on the sky plane and a specified number from either side of center. But unlike Irwins GE file, the Occult one does not include lines for the occultation by Dimorphos, so Irwins file is preferred. More about some of the upcoming Didymos events is below. For them, more observers are always welcome, to occupy more of John Irwin's Google Earth observer lines described above. If you are interested in participating in any of these events, contact me, dunham@starpower.net or 301-526-5590, to get a line assignment. For some events, Roger Venable, rjvmd@progressivetel.com, will be assigning the lines. _ _ _ 2023 JANUARY 1 DIDYMOS OCCULTATION 1h UT, Southwestern USA 1h UT, eastern North America 1h UT, southeastern Canada 1h UT, southwestern Europe 1h UT, n. Africa and Middle East This good occultation has already occurred. Unfortunately, cloudy skies plagued all of the path from which observers planned to try it. The cloud cover was so extensive in most areas that all observers except for Vadim Nikitin did not leave home to try the occultation. Vadim travelled to south-central Colorado, where he was able to acquire the target star and record it through the time of the occultation. But the observation was through rather thick and variable cloud at the expected event, and his recording is still being analyzed, to see if a real event might be detected in the very noisy recording. Under the circumstances, there was no chance to try for the Dimorphos occultation. _ _ _ ACROSSs Damya Souami noted a faint event, an occultation of a 15.1-mag. star by Didymos around 7:05 UT (2:05am EST) of Tues. morning, Jan 17th, visible from the northeastern USA with zoomable Aladin charts and other event details on Occult Watcher Cloud; for the zoomable Google map there, select the 2nd line (using the JPL#201 orbit) or directly, click here. The path crosses North America from coast to coast, but the current NWS cloud forecast shows that it will be very cloudy along most of the path, with the only predominantly clear area being the Hudson Valley and Conn. The path over the Hudson Valley and Conn. is shown in this map. I think only an 18-in. or larger scope might detect the 1/3rd-sec. occultation of this faint star by Didymos, and larger scopes would be needed for Dimorphos. The Occult input file, using the latest JPL201 orbit, for the event is here. Also showing clear sky in the Hudson Valley/Conn. area are the cloud forecasts of GFS and the Canadian weather forecast for astronomy. Probably this event was not observed; I have not heard from possible observers since the occultation occurred 2 nights ago. _ _ _ 2023 JANUARY 18 DIDYMOS OCCULTATION This is our next chance to record an occultation by Dimorphos with video but a large telescope, probably 12-in. or larger, will be needed to record the short Dimorphos occultation of this 13.1-mag. star. The path crosses the southernmost part to Arizona and southern Florida; it also crosses Texas and other south-central US areas, but the cloud cover forecast is poor for them. It looks good for Florida, and partly cloudy in aouthern Arizona, but maybe OK there with the high event altitude, nearly in the Zenith there. Occult map, Florida to Houston Occult map, Houston to southern Arizona cloud cover forecast Path across Florida Zoomed in map, South Palm Beach area Roger Venable, rjvmd@progressivetel.com, is coordinating observations for this event using this Path across Google Earth file from John Irwin, who writes about it here. Half a dozen observers have signed up for the event, and Roger plans to deploy a few stations. Email Roger if you might be interested in helping for this event. I have added the OWC links and some other information to Rogers Jan. 14th message here. Also, see this explanation of Irwins Google Earth file. Sky Plane diagrams of the Didymos-Dimorphos system for this event by John Irwin: Florida Arizona So far, I have not heard if this occultation was observed. _ _ _ 2023 JANUARY 21/22 DIDYMOS OCCULTATION This is our last really good chance to record an occultation by Dimorphos with video with relatively small telescopes; please join our effort to observe this occultation in Florida if you can. But the cloud forecast for Florida is poor, so we may cancel the effort there for this outstanding event. The European ECMWF, US GFS, and Canadian cloud forecasts are all similar to the NWS one, so it is very unlikely that any observations will be possible from Florida. We will need to depend on observations from Europe and possibly farther east. ACROSS is coordinating the observations in Europe with a special Web page they have set up using parallel "fence" lines that take into account elevation above sea level, like John Irwin's Google Earth files. this message about it by me and Paolo Tanga; it includes the OW cloud link, that can be used for Aladin star charts and other event details, but of course, use Paolo Tangas link for the path, and to select a line for your observation. Occult maps Florida, Jan. 22, 0h UT or 7pm EST s. Europe, Jan. 21, 23h UT s. Europe to India, Jan. 21, 22h-23h UT ECMWF cloud cover forecast maps for Europe and Asia; note these maps are from a US Web site that uses CST (Central Standard Time), which is UT - 6h: n. Italy to s.w. France w. Bulgaria to Croatia Middle East India Sky plane diagrams of Didymos and Dimorphos by Steve Chesley, JPL Florida France These use the recently-updated orbit of Dimorphos but they are essentially no different than the earlier sky plane diagrams. John Irwin has supplied this this Google Earth file; it is not completely redundant with Tangas interactive path since Irwins includes the predicted path for Dimorphos that Tanga does not have. Also, Irwins file extends the path east across India which Tangas does not reach. This document describes Irwins Google Earth file and its use, while this message is what John says about this event. _ _ _ 2023 JANUARY 23 DIDYMOS OCCULTATION This is mmostly a southern Canadian event; in the USA, only Washington state is crossed by the path, over the Seattle area, at 5:05 UT (or Sun., Jan. 22, at 9:05 pm PST). Occult map, Labrador to Lake Winnipeg Occult map, Ontario to s.e. B.C. and n.w. Washington The OW Cloud link; for the path, be sure to use JPL#201. In her message of Jan. 13, for this event, Damya Souami copied the OW Cloud link from the Jan. 21/22 event, so it is wrong, going to the earlier event instead. We have requested a sky-plane plot and Google Earth file for this event, in case there are some observers willing to try it; let me know if you might try it, to coordinate observations. _ _ _ 2023 JANUARY 26 DIDYMOS OCCULTATION I only found this good 10.6-mag. event on Jan. 15 with a new Occult search using JPL#201, now considered the best orbit for Didymos fitted to the 2022 Oct. – Dec. observations. The #201 orbit shifted by less than a km from the previous 200 orbit, so I do not know why this event was not found during my late Dec. search using #200. For this relatively bright star, the central duration is a nice 0.57s, so a central Dimorphos event should be more than 0.10s. The event altitude is >15 in Wyoming & higher westward. Occult map, Nebraska to British Columbia Here is the OW Cloud link; but for the path, be sure to use the JPL#201 map, but just for preliminary planning since it does not take into account elevation above sea level. Here is the Occult input file for the event. We have requested a sky-plane plot and Google Earth file for this event, in case there are some observers willing to try it; let me know if you might try it, to coordinate observations. _ _ _ 2023 JANUARY 28 DIDYMOS OCCULTATION Here is a last eastern US occultation, although rather faint at mag.. 13.4, so it requires a rather large telescope. However, with a central duration of 0.71s, integration can be used, with a central Dimorphos event about 0.14s so integration might be used to detect it with 10-in. scopes, if sky conditions permit. Unfortunately, the event occurs too soon after sunset to give enough dark time to deploy multiple telescopes. Nevertheless, I will let Roger Venable coordinate observation of this event; contact him at rjvmd@progressivetel.com if you might be interested in trying it. The event has a very high RUWE of 10.5, so the accuracy of the star position may be too poor to really predict this event. We are asking the Gaia team to look into this star; since the EDR3 release, hopefully there are enough new observations that a new solution for the star might be computed that would reduce the RUWE. Occult map, Newfoundland and s.e. Nova Scotia Occult map, Delmarva to s. Alabama Here is the OW Cloud link; but for the path, be sure to use the JPL#201 map, but just for preliminary planning since it does not take into account elevation above sea level. Here is the Occult input file for the event. We have requested a sky-plane plot and Google Earth file for this event. _ _ _ 2023 JANUARY 29 DIDYMOS OCCULTATION Like the Jan. 26th occultation, this 12.20mag. event was only found on Jan. 15. The occultation has a whopping 0.76s central duration, so a Dimorphos occultation could last 4 NTSC frames. The path actually passes over Washington, DC, but with an altitude of only 4 deg. In s.e. Michigan, the altitude is 10 deg., and increases farther west along the path. Here is the OW Cloud link; but for the path, be sure to use the JPL#201 map, but just for preliminary planning since it does not take into account elevation above sea level. Occult map, Nebraska to British Columbia Here is the Occult input file for the event. We have requested a sky-plane plot and Google Earth file for this event, in case there are some observers willing to try it; let me know if you might try it, to coordinate observations. _ _ _ The later Didymos occultations will e quite difficult to observe, most being too brief to record reliably with video. If anyone is interested in any of them, we can provide more information. _ _ _ OCCULT INPUT .XML FILES FOR 2023 IOTAs Occult4 program is a free comprehensive occultation prediction program for Windows systems. You can use it with the input files below to generate your own predictions for your observatory or region, as described in this .pdf document. It describes a prediction input file for planetary and asteroidal files called All2023.xml. You can use that file to generate local predictions for many mainly main-belt occultations, but you can replace it with the other files listed below to generate predictions for more occultations, mainly of fainter stars than shown on the maps, or for other parts of the world: When you open these files with your Web browser, you should get a display that looks like this. The larger files may take a couple of minutes to show this appearance, showing a messed-up display before then. Once the proper view appears, right-click anywhere on the display, then "Save as" to a directory on your computer; the best directory is the \Asteroid\ subdirectory in your Occult\ directory. For the 23 NEA events mapped and tabulated in the main .pdf document But these all use orbits from August 2022; for Didymos, better orbits are now available. Worldwide Didymos events to mag. 14 for 2023 (but using Aug. 2022 orbit). A new version using the current JPL orbit will be posted soon. Worldwide Didymos events to mag. 14 for 2023 Jan. 15 - Dec. 31, using the JPL#201 orbit, currently the best available. North American Didymos events to mag. 14 for 2023 Jan. 15 - Dec. 31, using the JPL#201 orbit, currently the best available. Worldwide 2023 events for our selected NEAs (except Phaethon) to Mag. 14 Worldwide 2023 events for Phaethon to mag. 14 _ _ _ _ _ _ BACKGROUND INFORMATION ABOUT NEA OCCULTATIONS Comprehensive PDC2021 paper on NEA occultations, .pdf Didymos occultations presentation for SBAG mtg., 2022 Jan., .pdf by D. Dunham SBAG27, 2022 June 7-9 Didymos occultations presentation for SBAG mtg., 2022 June, .pdf by D. Dunham ACROSS presentation for SBAG mtg., 2022 June, .pdf by Damya Souami _ _ _ _ _ _ ACROSS (Asteroid Collaborative Research via Occultation Systematic Survey) On 2022 March 1, the ACROSS team announced their project and Web site: It is our pleasure to introduce a new project for occultation campaigns: ACROSS (Asteroid Collaborative Research via Occultation Systematic Survey) https://lagrange.oca.eu/fr/home-across This campaign is led by the Nice Observatory (OCA) and the Aristotle University of Thessaloniki (AUTh), and funded by the European Space Agency (ESA). The goal is to support observations of occultations by NEAs, specifically the asteroid system composed by (65803) Didymos and its satellite Dimorphos. The focus is to obtain positive chords before and right after the impact date of the DART mission satellite, expected to impact Dimorphos on September 26th, the main objective being improving our knowledge on the orbit of Didymos such that we can track the change caused by the impact. A secondary group of objects being campaigned for is a potential set of fly-by targets of the Hera mission that will follow-up DART. Other promising NEAs are in our "training" list. We share through our web site two different sets of events: involving bright stars (V < 10), and a general prediction file (XML by WinOccult) for large telescopes (V<16), that can be checked for specific regions. You may also find there details on our project, news and results of ongoing campaigns and tutorials on how to attempt observations of NEA events. For priority events, updates are provided through the Occult Watcher Cloud (OWC) web site, under the "ACROSS" campaign tag. Specific campaigns will be advertised. It must be pointed out that, due to the nature of NEAs, these are fast events, both because they move fast in the sky, and because a good portion of the NEA database is comprised of small objects. Therefore, only those who can track fast events should consider attempting these events. It is also preferable that you have a mobile station, as these are events with very small shadow paths. The trade-off is that, if positive, they will allow us to greatly improve the orbit of a NEA. Two Didymos events already being worked on are a mag 10 event in Abu Dhabi on September 20th and a mag 13 event in Spain on August 25th, which are addressed in greater detail on our website, and we want to cover as much ground as possible. On behalf of every member part of this mission, we thank you in advance for your interest and your contributions, and we look forward to working with you. Best regards, ACROSS Team Coordinators: Paolo Tanga and Kleomenis Tsiganis Core Team: Damya Souami, Joao Ferreira, Alex Siakas, Lyu Abe, Rodrigo Leiva, Luana Liberto, Pascal Oberti ______ David and Joan Dunham, 2023 January 5; updated Jan. 6, 6pm EST, Jan. 16, and Jan. 19 e-mail: dunham@starpower.net cell phone: 301-526-5590