3rd Annual Progress Report

Submitted to the

National Aeronautics and Space Administration

for

Grant No. NNX08AR22G

"A NEO Search ProgramUsing the Pan-STARRS PS1 Telescope"

Program Manager: Lindley Johnson

For the period29 March 2010 to XX March 2011

Submitted by

Robert Jedicke & Richard WainscoatPrincipal InvestigatorsInstitute for Astronomy

University of Hawaii

1.Executive SummaryFor most of the time period covered by this report the PS1 telescope failed to perform at the expected level. While the PS1 survey officially began on 13 May 2010 the system did not discover its first NEO until 16 September 2010. The discovery rate was low till the end of January 2011 such that by that time the system had only recorded about a couple dozen NEO discoveries. But on the night of 30 January 2011 (UT) the MOPS team was given control of the surveying to showcase the system’s NEO discovery capability and it established a record by discovering 19 NEOs. The night’s success catalyzed changes in the general PS1 survey strategy that were implemented in the last half of February 2011. Bad weather and an unfortunate mechanical failure of the camera’s helium cooling lines then played a factor in reducing the NEO discovery rate from the end of February thru early March 2011. However, in the one-week period from 9-16 March 2011 PS1 reported 29 NEO candidates to the MPC. About 10 of them made it on the NEO confirmation page but only 2 are currently listed as PS1 discoveries. We are confident that a large fraction of the NEO candidates reported to the MPC are in fact NEOs – the reason that so few of them have become discoveries is because during that week the PS1 Image Processing Pipeline was particularly bad at processing the data in a timely manner. Most of the candidate NEOs were reported to the MPC 1-2 days after they were detected such that the tracklets provided insufficient leverage for followup.Despite the problems described above we are optimistic about PS1 NEO performance in the coming year. We believe that the PS1 survey strategy is now about as good as it can be for NEO discovery given the constraints of surveying for other science goals as well. We have seen major improvements in the image processing pipeline performance and expect data to be available to MOPS in a timely manner for the remainder of the year. In short, we believe that PS1 will be either the first or second NEO discovery system this year.The portion of this grant used to support PS1 Operations is mostly used to cover a small number of budget items such as the PS1 observers, power, etc. Much of the funding to PS1 Operations from this grant during this time period was not received due to PS1 not performing well. Furthermore, PS1 Operations was supposed to provide software support for MOPS that has not materialized so we

have used some of the original PS1 Ops funding to support a MOPS software engineer.MOPS continues to function well and rise to the challenge of processing the ever changing PS1 data stream.

2.Grant OrganizationThis grant is divided into two components:

2.1. PS1 Operations Support (PS1 OPS)This component of the funding is devoted to supporting the PS1 telescope operations. The PS1 telescope operations is currently being handled by the PS1 Science Consortium (PS1SC), a group of about a dozen institutions that contribute about $3M/year to support PS1 operations. Since this grant provides about $0.5M/year for PS1 operations (with numerous caveats) it implies that the NEOO program is supporting about 14% of the total operations cost. PS1 OPS covers all operational aspects of the PS1 facility including but not limited to observatory maintenance, training and arranging of observers, camera maintenance, surveying strategy, telescope support, the image processing pipeline (IPP) and delivering the image data products to the consortium through an image and detections database.The PS1 OPS funding from this grant are delivered directly from the co-PIs to a co-I, Ken Chambers, who is the PS1 Director in charge of all PS1 OPS. The NEOO funding is used to support a small and specific sub-set of components of the PS1 OPS.PS1 operations does not cover the operations of any ‘science clients’ i.e. scientific analysis and interpretation of the processed PS1 data.

2.2. Moving Object Processing System (MOPS) SupportThe MOPS is a PS1 science client that handles all aspects of identifying moving objects in the PS1 data. This includes but is not limited to linking transient detections provided by the IPP on a single night into ‘tracklets’, that are then linked across nights into ‘tracks’, which are then fit to orbits to determine if the detections are consistent with being a solar system object. If the detections are consistent with being the same solar system object the detections are added to the MOPS relational database. MOPS takes care of attributing tracklets to previously known objects and precovering orphaned tracklets when they can be associated with a newly derived object.

Roughly half of this grant’s funding is directed towards MOPS support to enable continued improvements of the NEO detection capability, monitoring of the system performance, modifications to work with the PS1 data as it evolves into a fully functional sky survey, NEO visual confirmation by ‘NEO Czars’, data quality checks, scientific analysis, feedback to the PS1SC on survey strategy efficacy, etc. The vast majority of the grant support is devoted to paying salaries for key MOPS personnel as described below.

3. NEOO Funding Profile

Figure 1 – Delivered and expected funding profile from the NEOO program on this grant. The original grant funding was for a total of $2,525,000 over 3 years. Delivery of the funds to PS1 was delayed for a number of reasons. The NEOO program manager expects to deliver the remaining funding during the first year of extension.

For the first six months of the one-year period covered by this report (roughly April 2010 thru March 2011 inclusive) this grant was underfunded relative to the expected profile. The NEOO program manager delayed delivery of the funding until PS1 demonstrated an ability to discover NEOs. The delivered funding to the MOPS component of the grant was higher than the OPS component because most of the problems with NEO discovery were due to PS1 operations upstream of MOPS.Late in 2010 we received an injection of funding because PS1 began finding NEOs and it appeared that many of the operational problems were being addressed (see below for details). Much of the new

funding was directed to PS1 OPS since that component of the grant was underfunded relative to MOPS as described above. More funding was delivered later in 2010 and early in 2011 and distributed between MOPS and PS1 OPS. The new funding was distributed between the components in favor of MOPS even though the original grant proposal stated that funding would be equally distributed between the two. This is because the proposal assumed that the PS1SC would provide a software engineer to MOPS to continue MOPS integration into the PS1 system but that engineer never materialized. Instead, MOPS began the process of hiring a new dedicated junior software engineer.

4.PS1 OPSA detailed status report on PS1 Operations as of 6 December 2010 is provided in the attachment PS1SC_Status_Report_December_2010.Chambers.pdf (Ken Chambers, PS1 Director, co-I on this grant, and de facto manager of the PS1 OPS component of this grant). It provides a comprehensive description of the state of the system at the end of 2010 and mentions how the Modifed Design Reference Mission (MDRM) will improve NEO discovery efficiency. The MDRM was implemented late in 2010 but by late January 2011 it was clear that it was not providing the expected jump in NEO discoveries. In February 2011 MDRM-b implemented and it does seem to be successful at increasing the NEO discovery rate to a respectable level (see section 5.5). Due to a string of bad weather and an unfortunate break in the camera’s helium lines in early March we cannot yet provide an accurate assessment of the expected improvement PS1 will see in terms of NEO discovery. In general, we are finding that on a clear night with an operational telescope we are managing to get 2-3 NEOs on the MPC Confirmation Page.

5.MOPS

5.1. MOPS Personnel supported by this grantThe following individuals’s salaries were supported wholly or in part by this grant during the period of this report (in alphabetical order):

5.1.1. Larry Denneau (Manager & Software Engineer) During the time period of this report 25% of Denneau’s salary was supported on this grant. Most of his time was spent commissioning

MOPS for operations with PS1 data. E.g. ensuring that the data reported to MOPS by PS1 was in the correct format for MOPS ingestion and trying to handle the very large false source detection rates.

5.1.2. Mikael Granvik (post-doc)Granvik was supported 100% on this grant throughout this report period until his employment completed on 4 March 2011. He has accepted a position at the University of Helsinki. In the absence of significant PS1 data he 1) developed a technique to measure PS1 asteroid detection efficiency 2) provided orbit determination support for PS1 asteroid identifications 3) worked on determining the number and orbital properties of transient natural Earth satellites 4) supervised graduate student Eva Schunova on a) identifying NEO families and b) simulating the production and detection of tidally disrupted NEO families and 5) assisted in the analysis of genetically related NEO pairs with colleague Dr. Shinsuke Abe and 6) was critical to implementing human visual confirmation of PS1 NEO candidates.

5.1.3. Eva Schunova (non-IfA graduate student)Schunova is a Ph.D. graduate student in the Faculty of Mathematics, Physics and Informatics at Comenius University, Bratislava, Slovakia. She received a Slovakian national scholarship to perform research anywhere in the world at a location of her choice and she approached us to work on NEOs and Pan-STARRS. Since she would cost no money we were happy to accept her help after confirming her abilities with her references. She arrived at the IfA on 22 April 2010 and was supported by her scholarship through mid-September. She has been working on determining whether any NEO families exist in the known NEO population using rigorous statistical techniques. We expect that it will lead to a submitted Icarus paper within a couple months. A follow-on paper where she will set limits on the rate of tidal disruption by close Earth approaches should be submitted well before the end of the year. She then decided that she would like to complete her Ph.D. work on the research she had begun with us and has obtained permission from her home institution to do so. Thus, Schunova has been supported since 22 Sep 2010 by this grant at a graduate student level to work on NEO families.

5.1.4. Denver Green (software engineer)Due to the PS1SC not providing PS1 software engineer for MOPS we advertised for a junior software engineer in Feb 2011. At the same

time Will Burgett, the Pan-STARRS Program Manager, offered us the option of buying 50% of their new MOPS software engineer to obtain 100% of his time. (Note that PS1 and Pan-STARRS are different entities.) We decided that this was a better idea, and provided a more experienced engineer in a timelier manner, than us hiring an engineer ourselves. Thus, Green began working on MOPS on 1 Mar 2011 under the direct supervision of the MOPS Manager (Denneau). We have developed a prioritized work plan thru the end of 2011.

5.2. Other MOPS PersonnelOther individuals who were critical to MOPS development, support and NEO research during this report year:

5.2.1. Tommy Grav (Johns Hopkins)Grav was an IfA post-doc working on MOPS for three years at its inception. He has remained active in following and contributing to MOPS development and was particularly helpful in applying his knowledge from analyzing WISE spacecraft data to PS1 this year.

5.2.2. Henry Hsieh (IfA Hubble Fellow)Hsieh is working with Kleyna (see below) to identify comets and especially main belt comets in the PS1 MOPS data. This work relies only on morphological parameters of the detection so they use postage stamp images centered on each of hundreds of thousands of detections to identify cometary activity.

5.2.3. Robert Jedicke (co-PI)Jedicke and Wainscoat continue to perform PI duties.

5.2.4. Jan Kleyna (IfA-NAI postdoc)Kleyna is working with Hsieh on main belt comet detection. In particular, Kleyna developed the MOPS postage stamp server that provides postage stamps for all detections that appear in tracklets that are 1) attributed to a known object, 2) in a derived object or 3) in a tracklet containing at least 4 detections.

5.2.5. Andrea Milani & others (University of Pisa)The MOPS team has relied heavily on many people through the years but Andrea Milani stands out above the rest as having made critical contributions to the system without financial compensation. He and Fabrizio Bernardi, Davida Farnocchia and Givoanni Gronchi spent 4

weeks at the IfA in Aug 2010 to refine their orbit determination software for use with MOPS and also to study opportunities for removing false source detections based on their morphological properties.

5.2.6. Richard Wainscoat (co-PI)Wainscoat and Jedicke continue to perform PI duties.

5.3. MOPS DevelopmentsMOPS has been a mature software system for many years that was simply waiting for PS1 data. Thus, relatively little MOPS development has taken place in many years. Instead, most of Denneau and Granvik’s time during this report period was spent trying to get PS1 data into a format that could be processed through MOPS. The PS1 data flow and quality changed dramatically every month or so and often from night-to-night due to image quality or other processing issues. The fundamental problem was/is the false source detection rate. For most of this report period the false detection rate was 10-100x larger than specified in the MOPS input requirements. There was little that MOPS could do to handle data with this false detection rate – instead, the PS1 surveying strategy needed to be modified to acquire 4 images at each boresite location to reduce the false tracklet rate to a manageable level. Even then, it was extremely rare to obtain 3 or more nights in a lunation with 4 images at each boresite so it was impossible to link tracklets across nights as MOPS was designed. Once 4 images were regularly acquired during surveying MOPS was quickly able to form tracklets containing 3 or more detections. Much to our disappointment, the false source detection density was still so high that on many nights there could be hundreds of false 3 or 4 detection tracklets – a set of false detections that appear to be real objects moving at a consistent rate between the image frames. The only way to ensure that we could extract real objects and fast moving NEOs from these tracklets was to initiate visual examination of each tracklet candidate. This was a disappointment to the MOPS team because it was contrary to the intended MOPS operations that were not supposed to require human intervention. Denneau quickly put together a ‘NEO Czar’ page to facilitate the examination process. It presents the user with postage stamps of the detections in each tracklet along with important information such as

e.g. the MPC NEO digest score, rates of motion, and whether the object is linked to a known object. We also set up a gmail NEO Czar calendar to coordinate who on the MOPS team would examine the tracklets. In the beginning, Denneau, Grav and Granvik did much of the czaring until the process was refined enough to train Wainscoat, Jedicke and Schunova. We are also in the process of training volunteers from the ‘Friends of the IfA’, a group of educated and eager astronomy enthusiasts who support the IfA financially and organizationally. The NEO Czaring page is also being improved and we expect that the entire process should take no more than 15-30 minutes per clear night.One of the problems with NEO Czaring is that the data from the PS1 Image Processing Pipeline does not arrive on a regular schedule. In theory the processed data should be available to MOPS before local noon but in practice it rarely arrives till late in the afternoon. This makes it difficult for the NEO Czar to process and report MPC candidates to the MPC in a timely manner. Despite the problems, PS1 began reporting NEO candidates to the MPC on 28 August 2010 and our first confirmed NEO discovery was 2010 ST3 on 16 September 2010. As of the time of writing PS1 has XX confirmed NEO discoveries including XX PHAs. We expect the discovery rate to increase even more in the first half of 2011 and then level out as the PS1 surveying finally settles into a consistent pattern.The quantum leap in PS1 and MOPS performance was catalyzed by the Pan-STARRS PI (Nick Kaiser) choosing to give the MOPS team one good dark night for a ‘NEO Demo Night’ to showcase what PS1 can do. NEO Demo Night is described in detail below (section 5.4) but its main effect was to show that PS1 could be extremely effective at identifying NEOs if the survey strategy was designed to find them. Based on the stunning success of NEO demo night PS1 adopted a more asteroid and NEO friendly survey strategy beginning in mid-Feb 2011 suggested by the MOPS team about six months earlier. While there is only limited data to support the efficacy of the strategy the first results look promising as shown in Figure 2.

Figure 2 – Left: eccentricity vs. semi-major axis for 2911 derived objects from early in 2010. Right: same distribution for 1266 derived objects from early in 2011.

Figure 2 shows the dramatic improvement in PS1+MOPS performance over the past year. The left side of the figure shows the results for derived objects, multi-night tracklet linkages, for ‘demo month’ in early 2010 while the right side shows the same distribution for derived objects using the latest PS1 surveying strategy implemented partway through Feb 2011. A year ago we were plagued by false detections that generated false NEO signatures for false tracklets and linkages. Now there are zero false NEO candidates in a sample of 1266 derived objects. The semi-major axis distribution in the main belt clearly shows the large scale structure of the belt including the n6 resonance that cuts off the distribution of objects on the inner edge and the mean-motion resonances that cause the lack of objects at about 2.5 and 2.9 AU. We identify Hilda’s at about 4 AU and several Jupiter Trojans near 5.1 AU.

5.4. NEO Demonstration Night1

In early January 2011 the Pan-STARRS PI, Nick Kaiser, invited the MOPS team and PS1SC Inner Solar System key project (KP1) to devise an observing plan for an entire night of observing using his PI discretionary time. The ‘NEO Demo Night’ would be dedicated to demonstrating PS1's NEO and PHO discovery capability. The night of 30 January 2011 UT was selected due to it being near new moon and the good weather forecast.

This grant’s co-PI Wainscoat devised an observing plan consisting of the evening and morning ‘sweetspots’ between 60-90 degrees solar elongation (the ESS and MSS respectively) and opposition solar 1 Thanks to Larry Denneau for providing much of the text in this section.

system fields (OSS) near the ecliptic and opposition (see Figure 3). The PS1 surveying was composed of 4-visit ‘quads’ to each footprint using 45-second w-band exposures. As a test at low surveying altitudes we decided to perform a small ‘chunk’ of r-band exposures at low solar elongation in the ESS. It was thought that the r-band might provide better image quality and depth at low altitude because of the decreased atmospheric dispersion relative to the wide w-band.

Figure 3 Realized surveying fields for NEO Demo Night on the night of 30 January 2011 UT. The solid light gray fields were observed while the empty gray polygons were optional fields. The chunk of fields on the right is the ESS, the large chunk of fields to the right of center are near opposition and the ecliptic, and the chunk of fields on the left close to the Sun are the MSS. The ecliptic is the red solid line and the galactic equator is represented by the blue solid line.

Overall, 596 exposures (432 near opposition and 164 in the sweetspots) were acquired at 149 different boresights covering about 1000 deg2. Everything operated very smoothly on NEO demo night with IPP processing the images nearly as they were acquired. By 9:16 PM HST 29 January 2011 we had submitted our first object to the MPC and the object was posted on the NEOCP and by late afternoon on 30 January 2011 HST about 20 objects had been

accepted to the NEOCP. A MOPS processing glitch held up processing of a couple OSS chunks until Monday yet by mid-Monday at least 30 objects were on the NEOCP.While the original design of the Pan-STARRS surveys was to provide self-follow-up of all asteroids this could not be accomplished during NEO demo night. Instead, we informed all our followup collaborators (in particular: Tholen & Michelli on the CFHT and UH 2.2m, Ryan at the Magdelena Ridge Observatory, McMillan at Spacewatch, Lister and Armstrong at the Faulkes Telescope and Las Cumbres Observatory, and Robert Holmes at Astronomical Research

Observatory) about the upcoming demo night and

Figure 4 – Maximum number of NEOs discovered at a single site in a single night for the 5 most prominent NEO survey programs. No other program discovered more than those shown in this figure. The month and year of the accomplishment for each program is given at the top of the program’s column.

forewarned the MPC. Unfortunately, the weather was poor on the mainland after the 29th so our follow-up partners were less effective than usual and a significant portion of the follow-up confirmation was left to Tholen and Michelli on the CFHT and UH 2.2m. Figure 4 shows that a total of 19 NEOs were confirmed as discoveries by PS1 on Demo Night, establishing a record for objects discovered on a single night at a single site. There were never so many candidates reported by a single site to the MPC NEOCP and we estimate that at least a few of the 11 objects that made it on the NEOCP but were not

confirmed were actually NEOs. Furthermore, we know that about an equal number of NEOs were ‘hiding in plain sight’ in the data (Jedicke AJ 111 #2, 1996) – they were detected but their rates of motion did not flag them as being NEOs. When PS1 implements the MOPS surveying plan we expect to extract those NEOs from the data as well. Finally, due to the remaining false source detections and the unavailability of trail fitting software, the identified NEOs were constrained to have rates of motion between about 0.1 deg/day and 2 deg/day so that we could not identify very close NEOs with long trails or NEOs moving at very small rates. Thus, despite establishing a single night NEO discovery record we suspect our NEO detection efficiency in the fields we observed was less 50%.

Figure 5 – Left: Main belt object detection efficiency as a function of apparent V magnitude in the ESS. Right: The same but for an OSS chunk. The solid line in both figures is a fit to the efficiency.

On the other hand, the main belt object detection efficiency was ~90% for objects that were well above the detection threshold (see Figure 5). Note the difference in the fitted efficiency curve in the ESS and OSS. The magnitude at which the ESS detection efficiency is 50% of the maximum is about V=22 but in the OSS the curve fades gently instead of fast and the same point occurs at about V=21.5. Ken Chambers, the PS1 Director and co-I on this grant, suggests that this effect is due to a known IPP bug related to the variance. (This problem has been fixed and the latest PS1 data is a vast improvement over what MOPS has processed in the past.)Andrea Milani's known_server software attributed over 18,000 numbered MBOs in the NEO Demo Night data or close to 200 asteroids per PS1 image footprint. There are likely another equal number of known unnumbered objects in the data as well as another

equally large number of unknown objects. Unfortunately, for various reasons these data have not yet been reported to the MPC.

5.5. MDRM-bThe second version of the Modified Design Reference Mission (MDRM-b) was implemented midway thru observing cycle (lunation) 136 – essentially the month of February. MDRM-b suggested by the MOPS team in September 2010 as a new surveying strategy that would have minimal impact on other PS1SC science but a dramatic improvement on the detection and follow-up of asteroids and especially NEOs. The first implementation of the MDRM (a) late in 2010 neglected to enable many of the key aspects of MDRM-b that we did not realize improved asteroid discovery capabilities. Furthermore, continuing bugs in the IPP processing exacerbated the surveying problems. However, with the catalyst of NEO Demo Night (Section 5.4) MDRM-bwas finally implemented. The strategy is illustrated in Figure 6.

Figure 6 – Schematic representation of the MDRM-bsurveying strategy.

The basic idea of MDRM-bis to obtain many more tracklets for each object in a single lunation such that at least one or two of the tracklets contains 3 or 4 detections. With the recent IPP bug fixes the probability that a 3 or 4 detection tracklet is real is nearly 100% and these tracklets can be used to ‘anchor’ the identification of derived objects – tracklets linked across nights within a single lunation. The right side of Figure 2 shows the very clean result of implementing this technique and the IPP bug fixes. The derived objects show zero contamination from false NEO candidates and all the derived orbits look real and give a snap shot of the solar system in the observation direction out to Jupiter.

5.6. MOPS SummaryThe MOPS continues to perform well and is adapting to the ever improving PS1 data stream. The system has demonstrated the ability to identify objects in tracklets on a nightly basis and to cleanly link tracklets across nights into derived objects.

Figure 7 – Total number of objects reported to the MPC in 2010. For various reasons PS1 has only reported known multi-opposition objects to the MPC and only for a subset of the available 2010 data.

Despite the numerous processing problems in 2010 Figure 7 shows that PS1 still managed to report observations to the MPC for a competitive number of minor plants. In fact, PS1 ranked 3rd in terms of the number of numbered+unnumbered objects reported to the MPC behind the WISE spacecraft and the CSS G96 site. It is important to note that PS1 has not reported all the available observations due to the processing problems described above – we

expect to report 2-3x more detections for 2010 after all the year’s survey data is reprocessed through the IPP and MOPS. It is likely that once all the available data is reported to the MPC that PS1 will take the lead in number of reported objects for 2010.PS1’s NEO discovery rate was not good until the end of 2010 but it continues to improve. We believe that the 2011 NEO discoveries reported to the MPC provide a better snapshot of expectations for the year (see Figure 8). But even the first few months of 2011 do not provide a good indication of what we expect from PS1 since it incorporates only a tiny portion of data acquired with the new MDRM-bsurveying strategy.

Figure 8 – PHAs and NEOs reported to the MPC in 2011

6.Outlook

6.1. FundingWe have filed and been granted a first year NCE request with NASA thru the NSSC No-Cost Extension Web Form. We have had discussions with the NEOO Program Manager who has indicated his

intention to respect the funding of the original grant and provide us the remaining $1050K in funds this year. We expect to receive $300K early in the year and the remainder late in 2011.

6.2. PS1 OperationsPS1SC Operations is approaching survey maturity from the standpoint of the NEO discovery program. There are a few issues to be resolved with e.g. fine tuning the 3pi surveying mode, resolving image processing delays that often provide data to MOPS 2-3 days late, and the remaining false source detection problems. But the issues are no longer shackling MOPS performance and we expect to see continued improvements that ensure MOPS will find even more NEOs thru the 1st NCE year.

6.3. MOPS The outlook for MOPS during the upcoming report period is excellent. The numerous improvements in PS1 operations will allow MOPS to operate close to the manner in which it was designed and we expect to report record numbers of minor planets, NEOs and PHAs to the MPC this year.With the promise of the remaining grant funding we are currently seeking a new postdoc and have 3 strong candidates. We expect to make an offer to one of them within days. We will also continue funding Slovakian graduate student Eva Schunova for her assistance with NEO czaring, data analysis and research. The shared funding of the Pan-STARRS software engineer, Denver Green, should allow MOPS to achieve its design goals by ensuring that the PS1 input data meets the MOPS requirements. We will hire a new junior software engineer late in 2011 to ensure a smooth transition to a new MOPS software engineer after Green reduces his time on MOPS effective 1 Jan 2012.