Spring 2018 RECON Update

The 2017-18 academic year started off strong with our Annual RECON Team Meeting in Sunriver Oregon in late October and an occultation event in November involving Centaur 01SQ73. However, since then we have not had any high probability TNO occultation events to pursue as a network.  We wanted to briefly explain why and share what we have been working on to address this.

Mayall 4-m Telescope at Kitt Peak National Observatory (credit P. Marenfeld & NOAO/AURA/NSF)

Up through January 2016, RECON Principal Investigator Marc Buie had successfully competed for routine use of the Mayall 4-meter Telescope at Kitt Peak National Observatory to monitor the positions and orbits for TNOs that feed into our RECON occultation prediction system. However, the Mayall Telescope has been undergoing a significant mission reconfiguration over the past two years to focus on the 3-D structure of the universe to investigate dark energy.

While this involves cool science, the downside has been that the facility is no longer available to RECON and other projects previously using the telescope facility. With the resulting loss of telescope time for monitoring TNO positions, we have seen a significant drop in our ability to predict high-probability TNO occultation opportunities this year.  Hence, no official, full-network RECON campaigns since November.

Apache Point Observatory in Sunspot, New Mexico

To address this, Marc Buie and Rodrigo Leiva at SWRI and John Keller (now at Fiske Planetarium at the University of Colorado Boulder) have been working over the past several months to obtain observing time on other telescopes to collect more positional data for our TNO prediction system. Toward that end, RECON was recently awarded 4 half-nights with the 3.5-meter telescope at Apache Point Observatory in New Mexico. Weather permitting, we hope to measure as many as 70 TNOs in April and May with this facility.

Gemini North 8-m Telescope in Hawaii

We have also obtained 4 hours for a pilot program with the Gemini North 8-m Telescope located in Hawaii. With this telescope, we expect to observe 5-6 TNOs, focusing on much fainter objects.

During the middle of March, we observed the first three objects of this Gemini study and analyses are on the way. Shown below is a stacked image of one of these objects taken at three different times during the night.  The white objects are stars, while the red, green, and blue dots are the the same object changing positions with each exposure, a TNO moving relative to the background stars!

Mosaic of three Gemini images showing position of moving TNO (red, blue, and green dots)

We also have monthly time allocated on the 4.3-meter Discovery Channel Telescope (DCT) at Lowell Observatory in Flagstaff, Arizona, and another proposal was recently submitted to observe more than a 100 TNOs with our Canadian colleagues at the 3.6-m Canada France Hawaii Telescope (CFHT) telescope.

Discovery Channel Telescope in Flagstaff, Arizona

Canada France Hawaii Telescope

 

 

 

 

 

 

Gaia spacecraft run by European Space Agency

Another important development coming up in less than a month is the second data release of the Gaia mission headed by the European Space Agency on April 25. This catalogue will provide ultra-high precision position and proper motion information for over 1.3 billion stars.

 

Because occultation predictions depend on known positions of both the target star and occulting object, both the Gaia dataset and our TNO monitoring efforts described above should get us back on track to our proposed cadence of 6-8 occultation campaigns per year by the start of the next school year.

So what should RECON teams expect before the start of summer? There are currently five potential TNO campaigns in our prediction system on the following four dates before the end of the school year (5/10, 5/24, 5/25, 6/8, all UT dates). Clear skies permitting, we plan to measure the positions of all five of these objects on April 16-17 from Apache Point Observatory (along with an additional 60ish objects). We will use this data and the Gaia dataset to update our prediction system by the end of April, and we will let our RECON teams know by early May if any of these five become high probability events that we would like to pursue. This is a classic example of how additional and higher quality data can used to obtain better predictions to drive further science.

Shadow path prediction for Pluto occultation on August 15 UT (provided by Lucky Star Project led by B. Sicardy)

Finally, looking ahead to the summer, it is also very likely that RECON will participate in an important occultation opportunity involving Pluto. This event will occur on August 15 around 05:32 UT, and RECON is very well positioned to provide valuable data during this event. Additional information on this and other TNO and Centaur predictions is available on the ERC Lucky Star Project prediction page.

 

 

Rodrigo and John are planning to blog from the Apache Point Observatory the nights of April 17 and April 18. We will keep you posted on how this observing run goes and the resulting impact on future TNO predictions.  Stay tuned!!

Lunar Eclipse Over Western Nevada

For those of you that weren’t able to view the early morning event, forgot about it, or maybe just didn’t care, I offer the attached composite image as seen from Gardnerville, Nevada. The lunar eclipse started around 11:48 UTC (03:48 PST) and the moon was completely within the earth’s shadow about an hour later. We had partly cloudy skies with varying levels of cirrus over the Carson Valley. The moon was approximately 36 degree above the western horizon at the start and set before coming completely out of the earth’s shadow. For those interested in the specifics of the captured images; each of the three images in the composite were taken with a Canon EOS 80D with a Tamron 150-600 mm G2 zoom at 600mm (APS-C sensor – 1.6 crop factor – 960mm equivalent focal length). Exposures for each of the images are: 1/500 sec. (left image), 1.6 sec. (middle image) and 4 sec. (right image) at f/6.3. The camera and lens system were mounted on an EQ mount for the last images due to the necessary length of exposure.

Daytime Occultation of Regulus by the Moon

Good luck to all of our RECON Teams on two occultation opportunities this month:

Also, on Saturday morning, November 11 around 17UT, the waning crescent moon will occult the star Regulus.  This event will occur during daylight hours for the western US, but through a telescope, with binoculars, or even just naked eye, you should be able to see both the moon and Regulus before the occultation occurs. The prediction map below shows the path of the moon’s shadow.  This map, along with predicted occultation time by major city, is also available at http://www.lunar-occultations.com/iota/bstar/1111zc1487.htm.

Shadow prediction for lunar occultation of Regulus

 

Switching Back to Standard Time

Just a quick reminder that all of our RECON teams outside of Arizona will be going off Daylight Savings this Sunday morning, November 6, at 2AM local time. In addition to giving participants an extra hour of sleep, turning clocks back will place the majority of our teams 8 hours behind Universal Time (UT) from now through March.

RECON teams should take care in converting UT times to local times:

  • Our Arizona teams remain on Mountain Standard Time = 7 hours behind UT
  • All other teams fall back onto Pacific Standard Time = 8 hours behind UT

All times listed on the Event Detail Page for 08FC76 are provided in UT and need to be adjusted for the correct time zone for each site. The event will be centered around 11:55 UT on November 23, 2016. Using the offsets above, this converts to:

  • 4:55 AM MST on the morning of November 23
  • 3:55 AM PST on the morning of November 23

All RECON Teams are reminded to complete the RECON Campaign Signup Form as soon as possible so that we can ensure telescope coverage for this Thanksgiving campaign!

 

Occultation of TYC 5780-01169-1 by (19) Fortuna

On 2016, August 13 at 06:30 UT, main belt asteroid (19) Fortuna occulted the star TYC 5780-01169-1 in the constellation Aquarius. Four RECON teams and two other observers recorded the event. A total of five teams actually observed an occultation and one team observed a miss. Observing a miss can be just as important as observing an occultation because misses help define the size of the asteroid. For a more comprehensive overview about the data analysis process for main belt asteroid occultations, see Tony George’s blog post from January, 2016.

Here is the path for the event, which passed over the northern part of the RECON network. Even if you don’t have access to the Occult Watcher program, occultation announcements and maps such as this can be found at the asteroid occultation website.

Map of 19 Fortuna's shadow path

Map of 19 Fortuna’s shadow path

Here are light curves from the three RECON teams that recorded an occultation. Note that the horizontal and vertical scales on each of these light curves are different.

Manson light curve of 19 Fortuna

RECON Manson, Jared Mumley

Ellensburg light curve of 19 Fortuna

RECON Ellensburg, Megan Rivard and Bruce Palmquist

The Dalles light curve of 19 Fortuna

RECON The Dalles, Bryan Dean

Occultation scientists, such as every member of RECON, can use these light curves to determine the disappearance and reappearance time of the occulted star. IOTA, the International Occultation Timing Association, uses these disappearance and reappearance times, along with the location of the observers to estimate the outline of the asteroid.

Each of the chords in the plot below shows when and where the target star is visible. When the asteroid occults the star, there is a gap in the cord equivalent to the amount of time the star disappeared. When all of the chords and gaps are combined, you can start to see the size and shape of the asteroid. The gray area shows a model of the asteroid’s shape based on existing data. Notice how chord 1 fits the model almost exactly while chord 4, measured by RECON Ellensburg, starts and stops inside the predicted shape of the asteroid model. This could indicate a slight error in Ellensburg’s timing. But it could also mean that the actual shape of the asteroid is a little narrower along that line than predicted. Less likely but still possible, there are deep indentations in those portions of the asteroid. Chord 7, measured by RECON The Dalles, has a very small gap indicating that just the tip of the asteroid occulted the star.

Shape of 19 Fortuna according to current models

Click on the image above for a higher resolution view of the plot.

Main belt asteroid occultations are a great way to train new RECON participants in occultation science. One of the main reasons for this is that you can often see the target star and the asteroid. So even if your site does not record an occultation, you can still observe the dynamic nature of the Solar System by watching the asteroid move towards and then away from the target star.

Credits: We give a big “Thank You” to Tony George for generating and extracting precise timing information from our light curves.

Lassen Dark Sky Festival

This past summer 12 RECON team members participated in the 4th annual Lassen Dark Sky Festival in August of 2015. Members helped conduct stargazing and discussions about astronomy with over 4,500 visitors.  Since 2012, thousands of spectators visit Lassen national park every year to celebrate special astronomical events including the annular eclipse, the transit of Venus and the Lassen Dark Sky Festival.

Visitors can participate in various activities throughout the festival:

Lassen National Park is a sanctuary of natural darkness and offers spectacular views of the night sky.

Check out our RECON Team members at the Lassen Festival.

Check out more pictures of the Lassen Dark Sky Festival here.

Here are future events dates at Lassen National Park:
August 12-14, 2016 -100th Anniversary of National Park Service and Lassen Festival
August 11-13, 2017  One week before the total solar eclipse
August 3-5, 2018  James Webb Space Telescope launches in October

Documentation of occultation of 2UCAC 39956822 by (86) Aegle

The last positive occultation captured in North America in 2015 was the occultation of the star 2UCAC 39956822 by the asteroid (96) Aegle.  Overall, there were 8 observers who observed the event.  There were 7 positive observations and one miss observation.  Three of the positives were recorded by RECON team members, Chris Patrick, Steve Bock, and Tony George.  This blog will document the data contributed by the RECON members.

Here is the path map for the event.  You can see the path crosses through central Arizona and southern Nevada, where three RECON members are located.  Other observers in Arizona and central California were also able to observe the event.

Light Curve Analysis

All videos were uploaded via DropBox to an IOTA repository.  DropBox is a tool used by IOTA for capturing and exchanging video files.  Each of the video files were then analyzed by Tony George using Limovie.  Limovie is a tool for commonly used by IOTA for video light curve analysis.  Here are the three light curves that were captured by RECON members:

Chris Patrick

(96) Aegle 2015-12-30 Chris Patrick.ROTE.sqWave

Steve Bock

Aegle 20151229 Mt Potosi PSF TG.ROTE.blockint.detrended.sqWave

Tony George

(96) Aegle 2015-12-30.ROTE.detrended.sqWave

These three light curves have some interesting characteristics that should be noted.

The Chris Patrick light curve is very erratic and during the event, a very flat and uniform bottom.  These are characteristics of the camera settings, which did not match the standard RECON guidelines.  Whenever observing asteroidal occultations, RECON guidelines should be used for camera settings unless otherwise directed by the campaign organizer.

The Steve Bock light curve looks very ‘skimpy’.  Again, this is the result of camera settings, most significantly, the degree of sense-up that was set.  Steve used a sense-up of 64x.  This integrates 32 frames which means that each block of 32 video frames looks essentially the same.  Integration also cuts down on the amount of variation between individual frames and blocks of integrated frames. A sense-up of 64x is a common RECON guideline for TNO occultation observations, however it may be too much integration for use in brighter asteroid occultations.

When compared to Tony George’s light curve, you can see the degree to which a high sense-up can affect the look of the light curve.  Tony used a sense-up of 2x.  This integrates two video fields into one frame, so there are 30 frames per second that are all independent of adjacent frames.

While Tony’s light curve might not look good, it actually is the best of the three light curves for determining the correct D (disappearance) and R (reappearance) times from the video.  That is because integration (sense-up) averages the video data and the D or R might occur somewhere within the integration block and the actual time must be estimated from the brightness value of the block of frames.  With Tony’s video, the times can be derived to times less than 1-frame accuracy.

Occultation Disappearance and Reapperance Analysis

Once each video file was analyzed in Limovie, a data file is created in a comma separated variable format (csv).  That csv file can be analyzed by different software applications to search for hard-to-find occultations, however this occultation was easy to see.  The software programs can also be used on easy-to-see occultations, particularly those with video integration, so that more accurate estimates of the D and R times can be derived.  Tony George used the program R-OTE (R-code Occultation Timing Extractor) to analyze all three light curves.  The D and R times were determined and provided to the observers so they could send in their reports on a standard Excel spreadsheet provided by IOTA.  For those that have OccultWatcher on their computers, the Excel form is easily available through a reporting app in OccultWatcher.

Asteroid Profile Analysis

Once the various observation D and R times are sent to IOTA  for analysis, a powerful program called Occult4 is used to combine the times and geographic coordinates to determine the size and shape of the asteroid.  For each observer, a chord across the earth is developed indicating where and when the star was visible.  Where the star disappears, there is a gap in the chord equivalent to the length of time of the disappearance.  When multiple chords are combined, the gaps in the chords trace out the size and shape of the asteroid.  Here is the profile developed for the (96) Aegle event:

20151230_AegleProfileUpdated

Note:  Click on the above image to get a high-resolution view of the plot

The chords of observations by the various observers are shown in different colors.  The chords of the three RECON observers are Chord 1: Chris Patrick; Chord 2: Steve Bock; and, Chord 5: Tony George.  You can see from this plot the rough outline of the size and shape of the asteroid.  Superimposed on the plot of the chords is the ellipse of best fit to the openings in the chords.  The size of the asteroid as determined by this analysis is and ellipse with major axis of 169.6 km and minor axis of 163.0 km.  This is one of the best observations ever obtained of the asteroid (96) Aegle.  While this is only one snapshot of the asteroid on the date of the observation, future observations can determine the size and shape from other perspectives and hence the volume and density of the asteroid can also be determined from amateur astronomer observations.  This type of data is very helpful to astronomers and space scientists as they continue to characterize the main belt asteroids and try and made decisions on asteroids to visit on future space flights.

RECON Observations Were Critical to Getting Size and Shape of (96) Aegle

The determination of the size and shape of an asteroid by occultations requires a good spread of observers across the path.  In the case of the (96) Aegle event, the two Chords collected by RECON members Chris Patrick and Steve Bock were critical in setting the northern limb of the asteroid.  Without those two chords, the true size and shape of (96) Aegle could not be determined from the other chords.  This shows that occultation astronomy is a team sport.  It takes a variety of observations to get the size and shape of an asteroid.

Opportunity to Participate in Future Main Belt Asteroid Events

While not a focus of the RECON project, RECON members can participate in the observation of main belt asteroids to sharpen their skill in doing occultations.  The probability of getting a positive with a main belt asteroid event is higher for those within the path, since the orbits of main belt asteroids are better known than TNO’s.  In the future, Tony George will be sending out alerts for main belt asteroid occultations predicted to cross the observing sites of RECON members.  Typically, for a large main belt asteroid, the path may go over 3 or 4 RECON observers in the network.  Watch for postings of favorable main belt asteroid events on the tnorecon email list.  With luck, we will see your groups chord on a future profile plot.