2022 Occultations by Near-Earth Asteroids - Updated 2022 December 18
9.4-mag. occultation by NEA Geographos Dec. 12-13, TX to NY to NS
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 2022
The first occultation by Dimorphos, Didymos' moon, recorded on Nov. 12; need more
These occultations are described and illustrated (with maps and tables) in this .pdf document. IOTA will have campaigns for some of the last 2022 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 Dec. 12-13 Geographos event, and the 2022 Dec. 16th, 19th, and 23rd, and 2023 Jan. 1st (2022 Dec. 31st local date in North America) Didymos occultations. The results of past NEA occultations are posted on IOTAs asteroidal occultations results Web page for 2022. For example, scroll down to the Nov. 12 line for Didymos to see the sky plane plot, predicted path, and maps of observers sites for the first observations of occultations by both Didymos and Dimorphos. Some of the links below may be broken since we remove files for past events that we think will no longer be needed. If there is one you want to see, let us know and we will email the missing file to you. 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 Nov. 12, occultations by both Didymos and Dimorphos were recorded in southern California. We are trying to get observations of a few more occultations by Dimorphos; please help us with these efforts. By about March 2023, Didymos will recede from Earth so far that diffraction smearing will prevent observation of their occultations. Success before that will allow a much 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. You should read Roger Venable's Call for Observations for the two July events. for background information suitable for the future events, although much of the information there is superceeded by that above. 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. However, we have GE files from Herald for the North American events through the 2023 Jan. 1st occultation, but we do not have all of them yet from Irwin. 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. _ _ _ 2022 DECEMBER 12-13 GEOGRAPHOS OCCULTATION On Dec. 5, I forwarded OW Cloud (OWC) links for this event (and others) from ACROSS, which found the event, to several potential observers, but not to the IOTAoccultations list. Observers were encouraged to travel to the path and try to record it; a couple of them planned to try it. But it was cloudy over most of the path and nobody was able to observe the occultation, as far as I know. (1620) Geographos has a good orbit, helped with radar observations in 1994, and it is the most elongated object in the Solar System, with a potato-chip shape with dimensions 5 x 2 x 2 km. Occult maps showing the path, and the OWC link, are below. Texas to s. Missouri s. Missouri to w. New York w. New York to Nova Scotia Derek Breit has set up an "old-style" Google map page, and Steve Preston also now has a page for the event, including his usual finder charts, etc. For the zoomable Google map and Aladin star charts, visit OWC for the event; also other details, such as the expected duration (0.27s). On OWC, use the default (JPL#710) Google map. If you click on a location on the Google map, the predicted event time there, and the alt. and azimuth of the star, will be displayed. _ _ _ 2022 DECEMBER 16 DIDYMOS OCCULTATION Houston to cen. Colo. cen. Colo. to s.w. Brit. Col. OW Cloud link but for the proper small errors, you should use the JPL#199 Google map. A Google Earth file was provided by John Irwin, and a sky-plane plot showing Dimorphos by Steve Chesley. Three observers tried the event in Colorado and Texas, and although they all managed to find clear skies, they each had problems that prevented recording the occultation. Richard Nugent thinks he saw the brief occultation on his screen, but the recorded file apparently was lost when he tried to transfer it from the SD card he used. _ _ _ 2022 DECEMBER 19 DIDYMOS OCCULTATION S. Carolina to s.e. Minn. s.e. Minn. to n. Sask. OW Cloud link but for the proper small errors, you should use the JPL#199 Google map The current NWS forecast shows clear skies over the Carolinas, but it looks like it will be quite cloudy farther northwest along the path. Google Earth file from D. Herald Google Earth file from J. Irwin The sky plane geometry is very good for detecting an occultation by Dimorphos with large-enough scopes: Didymos system sky plane plot by S. Chesley Didymos system sky plane plot by J. Irwin If you might want to try to observe this, please inform Roger Veneable at rjvmd@progressivetel.com, he is coordinating the line assignments for this event. _ _ _ 2022 DECEMBER 19 SW-1 OCCULTATION Also tonight is an occultation by the giant comet SW-1 over San Diego, Puerto Penyasco, and near Monterrey, Mexico. Some fading by material (possible jets, etc., from a late Nov. outburst) ejected from the nucleus might be observed as much as 300 km from the (accurately updated) central line; for details, see the the Arizona occultations page that was updated Dec. 15. On that page are two charts showing the FOV for an 8in SCT, including a note about a minor labelling error on those charts. Since that update, I have created two zoomed out charts given below, not available anywhere else: Finder Scope view Naked Eye view _ _ _ 2022 DECEMBER 23 DIDYMOS OCCULTATION S. Carolina to s.e. N. Dakota Iowa to n. Sask. OW Cloud link but for the proper small errors, you should use the JPL#199 Google map. A Google Earth file has been requested from John Irwin, but for now, we only have the one from Dave Herald. The sky plane geometry is very good for detecting an occultation by Dimorphos with large-enough scopes: Didymos system sky plane plot by S. Chesley If you might want to try to observe this, please inform Roger Veneable at rjvmd@progressivetel.com, he is coordinating the line assignments for this event. _ _ _ 2022 DECEMBER 29 DIDYMOS OCCULTATION World Map South Texas Summary and path data OW Cloud link but for the proper small errors, you should use the JPL#199 Google map. Steve Preston has a page with his usual finder charts and other event details. Derek Breit's zoomable Google map was used to generate the South Texas map above, but DO NOT use it for locating stations; the Google Earth file noted below is more accurate, taking into account the small shifts due to elevation above sealevel, so it should be used with Google Earth instead. A Google Earth file has been requested from John Irwin, but for now, we only have the one from Dave Herald. The sky plane geometry is not great for detecting an occultation by Dimorphos, but it should be possible, showing as a bump on the south side of Didymos, according to this Didymos system sky plane plot by S. Chesley. So we need those with larger scopes with video cameras, to record the short event by Dimorphos from a couple of locations just south of the predicted southern limit, taking into account the ellipsoid models projected on the sky plane in the diagram. Both objects line up well with the motion, prolonging them, so the duration for a central Didymos occultation should be 0.53s (16 NTSC frames) while it should be 0.11s, or 3 NTSC video frames, for Dimorphos. Telescopes of 8-in aperature or larger I think will be able to record the Dimorphos occultation of the 10.6-mag. star, with reasonably good conditions. The plot by Chesley shows that the Dimorphos offset (in the sky plane) is about 370 m to the south, while the width of the object will be only 150 m. So I recommend that two stations try to record the Dimorphos event, located at 320 m and 420 m (in the sky plane) south of the Didymos center. That would be on the 3.2nd line south and the 4.2nd line south, of the fence lines of Dave Herald's GE file. There should also be s station near the northern limit of Didymos. Measuring the diagram more, I find that the northern limit should be 400 m north of center in the sky plane, or the 4th of Herald's fence lines north. To be sure to have a positive, with the uncertainties involved, for one station, I would put it at 250 m north of center, or on Herald's line 2.5 north (some interpolstion will be needed to achieve fractional parts of lines, but that can be done by eye, you don't need to measure it). It would be useful if another chord across Didymos could be obtained, but there may not be enough stations to do that. If you might want to try to observe this valuable event, please inform me at dunham@starpower.net, I will be coordinating the line assignments. Richard Nugent, rnugent@wt.net, says he wants to try it, if the weather forecast is good enough. _ _ _ 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 A Google Earth file has been requested from John Irwin, but for now, we only have the one from Dave Herald. Using it, I have created the two maps below of the path in the Phoenix region: Greater Phoenix region, Arizona Northern Scottsdale area, Arizona OW Cloud link but for the proper small errors, you should use the JPL#199 Google map. Clicking on the OW Cloud Google Map gives the event UT and circumstances at that point. The geometry is not ideal for detecting Dimorphos, but not impossible, as shown by this diagram by JPLs Steve Chesley for the USA. In Europe, Dimorphos has moved some, as shown here. By covering the northern limit region with larger telescopes, it should be possible to detect the Dimorphos occultation, but coverage should be enough to also cover the southern limit area, for a good solution for both objects. Closer to the time of the event, I will give guidance for this event like I give for the Dec. 29th occultation above, and soon we may also have the GE file with Dimorphos path from John Irwin. _ _ _ OCCULT INPUT .XML FILES FOR 2022 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 All2002.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 18 NEA events mapped and tabulated in the main .pdf document But these all use orbits from August 2021; for Didymos, better orbits are now available. Worldwide Didymos events to mag. 14 for the rest of 2022. It uses the latest JPL orbit #199 from Horizons for Didymos; it fitted well all of the Didymos occultation observations made through Nov. 15. Worldwide Didymos events to mag. 12 for all of 2022, in case you want to see the brighter past events, but it was created in Dec. 2021 so it is not as accurate as the current JPL orbit #199. Worldwide events for selected NEAs to mag. 14 Worldwide events (24) for Phaethon, late 2022 _ _ _ _ _ _ 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 Unistellar presentation for SBAG mtg., 2022 June, .pdf by Paul Dalba NASA's Small Bodies Assessment Group (SBAG) held their 27th meeting in Washington, DC and online 2022 June 7-9; links to the slides for three occultation presentations, two primarily on the upcoming Didymos occultations, are above. There were several other interesting presentations, given in the meeting agenda. In a talk about the Minor Planet Center, occultations were stressed as a major improvement of their new ADES reporting format, as shown in this slide, showing the light curve of an occultation by Phaethon recorded at high speed with a portable 1m telescope in October 2019. The status of several operating and soon-to-be-launched (notably Psyche) missions were given. During the Lucy presentation, Hal Levison showed the interesting results of the March 27th Polymele occultation. Different NEA radar programs were described; in the one about Goldstone, Marina Brozovic showed the upcoming close approaches that they plan to observe. On Dec. 27, the 200m asteroid 2010 X15 will pass only 0.0052 AU from Earth, providing what will likely be the best radar opportunity of the year. It may also provide a good opportunity for occultations; the radar observations should provide a high-accuracy orbit that we can use to predict occultation paths. I hope we can mount efforts for that event, but our priorities in late December need to be for the Leucus occultations that occur then, as shown in the map and table in this document and the 2023 Jan. 1 occultation of a 9th-mag. star by Didymos shown in the NEA occultations document. The link to my SBAG talk on Didymos occultations above has maps and some information about IOTA's campaigns for NEA occultations that will occur on June 25, July 20, July 24, Aug. 3, and Sept. 3. Also, in the NEA occultations document, it shows an occultation by NEA (3122) Florence on Aug. 16 that we plan to use primarily for training around the 2022 IOTA meeting that we hope to conduct the previous weekend. It mentions an occultation in Hawaii on September 15; the Occult map for it is here. Hopefully, we'll have some success with the earlier Didymos events so that a few local observers can observe the Sept. 15th event; IOTA doesn't have the resources to send multiple observers with large-enough scopes from the msinland to cover the event well. _ _ _ _ _ _ ACROSS (Asteroid Collaborative Research via Occultation Systematic Survey) On 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 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 _ _ _ Shortly after, I wrote [but updated Nov. 2022]: The Didymos occultations are all very short now, and they were less than 0.07s in duration through 2022 May, so yes, those were very challenging. However, now the durations are over 0.30s, so they can easily be recorded with our usual video systems. The durations are still 0.25s at the end of the year. IOTA will also be pursuing these events. We look forward to fruitful collaborations on these interesting events. We will be announcing some of the IOTA campaigns soon. _ _ _ April 2022 ACROSS announcement We have recently updated our predictions of NEA occultations both on our website (https://lagrange.oca.eu/fr/prediction) and in OccultWatcher (https://cloud.occultwatcher.net/events/campaign/ACROSS). For the first set, February and March, we failed to account that a lot of events would not be observable in any landmass, resulting in flooding OccultWatcher with unusable occultations. Steps were taken to make sure this doesn't happen, and the feeds for April and May were filtered to only include events with viable observability. The unfiltered sets of predictions can still be found on our website. At the end of each month, we will be updating our predictions on both sources, and we will send a reminder for anyone interested to participate in our campaigns. Best regards, ACROSS Team ______ David and Joan Dunham, 2022 January, updated April 17, May 22, June 10, 13, 21, and 24, and 18, August 20, September 9, November 11, and December 1, 10, and 18 e-mail: dunham@starpower.net cell phone: 301-526-5590