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Radar Characterization of NEAs: Moderate Resolution Imaging, Astrometry, and a Systematic Survey
James E. Richardson, Patrick A. Taylor, Edgard G. Rivera-Valentin, Linda A. Rodriguez-Ford, Luisa F. Zambrano-Marin (Arecibo Observatory), Ellen S. Howell, Michael C. Nolan (U. Arizona), Jon D. Giorgini, Lance A.M. Benner, Marina Brozovic, Shantanu P. Naidu (JPL), Jean-Luc Margot (UCLA), Michael W. Busch (SETI), Michael K. Shepard (Bloomsburg U.), Christopher Magri (U. Maine at Farmington), Sean E. Marshall (Cornell), Adam H. Greenberg (UCLA), and Jenna L. Crowell (U. Central Florida)

1 Introduction
NASA supports the planetary radar program at Arecibo Observatory to observe Solar System objects for 800 hours per year, at least 500 hours of which is allotted for near-Earth asteroids (NEAs). Our usage has been close to, but below, this expectation: 601 hours in the last year, with 483 hours for NEAs, and 117 hours for the Moon, main-belt asteroids, comets and planets. To reach our goal, we separate our NEA radar time request into two parts: the best imaging opportunities (Taylor et al.) requesting 300 hours and this proposal covering the second-best (lower signalto-noise ratio; SNR) imaging opportunities, radar astrometry targets, and systematic survey time requesting 300 hours as well. We stress that this delineation (by predicted SNR) is based on estimates of the size and rotation rate of the asteroid, either of which can be off by factors of several. Newly discovered objects sometimes offer excellent imaging opportunities, and we retain the flexibility to include these whenever possible as urgent proposals. In the last year, 53 hours, or 11% of the NEA observations were carried out as urgent proposals. Our previous asteroid detection statistics are outlined in Figure 1.

2 Scientific and Technical Justification
The motivation to observe objects other than the highest SNR imaging opportunities is that scientific value does not scale simply with SNR. At NASA headquarters the interest is in characterization and astrometry for orbit refinement of the smaller, lesser known objects that are potentially hazardous asteroids (PHAs), might be good human mission candidates (NHATS), or are suitable for a retrieval (ARM) mission. We try to comply with as many of these observing requests as possible. Our monthly survey frequently includes many of these targets. The observations requested here (309 total hours) are divided into three parts: 1. Moderate resolution imaging targets (predicted SNR/scan > 20, SNR/track > 100). The observation of 19 objects (112 hours) is requested. 2. Astrometry targets for orbit refinement (predicted SNR/scan > 5, SNR/track > 20). The observation of 2/3 of 39 objects (80 hours) is requested. 3. Systematic, 8-hour survey time-blocks, for the purpose of observing newly discovered objects. The conduct of 13 surveys (117 hours) is requested.

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Figure 1: (left) The number of NEA observations attempted, NEAs detected, and potentially hazardous asteroids (PHAs) detected are shown by year illustrating the increase in attempts and detections starting in 2012 following increased NASA funding. Detecting more objects requires observing smaller and fainter objects, which leads to an increase in non-detections, but also informs us about the parameters we use to estimate the SNR of a potential target. We assume rotation rates of 2.1 hours for objects H<25 and 0.5 hours for H>25. The actual sizes (range depth) vary widely, suggesting that the albedo variation may also be larger for smaller objects. (right) Same as on the left, but for NHATS objects or human-mission candidates. These objects are often very small (meters or tens of meters) and very challenging, often are near the threshhold of detection, so the fraction of successful attempts is smaller. However, these are of very high priority to NASA headquarters, so we attempt observations of as many as possible.

The scientific motivation for all of these are similar: improve the characterization of the NEA population, particularly the smaller objects (H magnitude > 23 or approximate diameter < 50 m). (Note: the H magnitude is the absolute brightness of an asteroid placed at zero degrees phase angle, 1 AU from both Earth and Sun, for convenience. It is used as a proxy for size. The visible albedo can vary by a factor of several (0.02-0.5) and affects the diameter as the square root of albedo.) Even low resolution images (5-20 pixels or so) can constrain the size of the object and distinguish spheroids from elongated objects or contact binaries and identify binary or multiple systems. A single radar observation can give a good estimate of the rotation rate and separate rapid rotators from very slowly rotating ones. This gives an indication of the internal structure and information about the collisional processing and the size at which a transition occurs from rubble pile to intact rock. Coordinated programs to observe radar targets at other wavelengths, from visible to thermal infrared, provide additional clues of composition and thermal properties, which in turn help to define the source regions of the NEAs. Characterization has lagged far behind discovery, so collection of basic parameters on a wide range of objects is as important, if not more so, than studying a few of the high SNR objects in detail. A balanced program towards each of these goals is proposed in the two NEA proposals submitted for observations in 2016 (a few objects in Jan 2017 are included to inform scheduling). Figure 2 (left) shows the rotation rates derived from radar observations compared to those taken from the lightcurve database (Warner et al., 2009). There is general agreement in the overall distributions from the two techniques, but radar measurements of NEAs can be made during a single observing track, often within minutes of observation, which is often an advantage. The 2


Figure 2: (left) Radar observations of NEAs (green and red) and lightcurve observations (black and grey) generally agree although the radar rotation is an apparent frequency projected into the line-ofsight. Radar measurements in red are confirmed by lightcurves; green points are apparent rotation rates and could be shifted vertically. The diameter scale at the top assumes an S-complex albedo of 0.2. (right) For the number of seconds of round-trip light-time given by the red numbers at the top of each region, objects are detectable in the region below and to the right of each line. The topmost line is an arbitrary bandwidth limit of 100 Hz that encompasses the NEA population.

spin limit at about 2.2 hours (10 rot/day) is clearly seen for objects with H < 21. Binary asteroid primaries are nearly all found along this boundary. At about H=21, objects begin to appear which can spin much faster without coming apart. Slowly rotating NEAs are very difficult to see using lightcurve techniques, because the object is simply not observable long enough. Radar observations are sensitive to these slow rotators, and we are beginning to see more of them. The spin distribution will place limits on the effectivness and timescale for spin-up by YORP, an effect of solar energy absorption and re-radiation asymmetry (cf. Bottke et al., 2006). The detectability of an asteroid using radar depends on several factors: distance from Earth (to the inverse fourth power), the object size, rotation rate, sub-Earth latitude, and reflectivity. The first is most important, but size and rotation are also important factors. The sub-Earth latitude is almost never known in advance but is assumed to be 0 degrees. In Figure 2 (right), an object at a roundtrip light travel time (RTT, red number in seconds) at the top of each black line can be detected in 15 minutes of observation if it lies below or right of the black lines. All PHAs are detectable at about 60 seconds RTT or less, while all NHATS objects are detectable at about 20 seconds RTT or less. Objects closer than 6 seconds RTT require a separate receiving station because of the time required to switch from transmit to receive.

3 Moderate Resolution Imaging Targets
Figure 3 shows two examples demonstrating that we can determine basic shapes, sizes, rotation rates, radar reflective properties, and refine the orbits of moderate (non-high-resolution) imaging targets in a relatively short amount of observing time. These objects are subsequently added to our statistical NEA properties database, which now includes over 400 objects. This slowly accumlating database is aiding us greatly in characterizing and increasing our understanding of the near-Earth 3


Figure 3: Two examples showing that we can determine basic shapes, sizes, and rotation rates of our moderate moderate imaging targets in a short amount of observing time. (left) 2007 EC is about 120 m in diameter, is roughly spheroidal, and rotates in 4.6 hours. (right) 2003 NZ6 appears to be a contact binary with two lobes, each 300 m or so in diameter, and rotating once every 13.5 hours.

asteroid population as a whole, giving us an accurate snapshot of the current state of its members, and providing clues as to its history and continued evolution. Table 3 contains a list of the 19 objects expected to result in moderate-resolution images, and we would like most of these to be scheduled, with 2 days for each target. Those expected to be higher SNR should result in higher resolution images, so additional days may be requested, as needed after initial characterization. Those of lower SNR will be adequately characterized to the extent possible in two days. If all of these are scheduled (19 objects at 2 days each), this is approximately 112 hours, including transmitter warm-up time. Note that some objects (annotated with an `A' in the notes column, will require additional optical observations during this apparation and prior to radar observation, to ensure an adequate orbital solution and ephemeris for telescope pointing.

4 Astrometry Targets
During 2014, astrometry corrections were provided by Arecibo Observatory for 95 asteroid objects, consisting of 118 delay (range) measurements, and 98 Doppler (velocity) measurements. Arecibo astrometry led to improved trajectory knowledge that permitted the removal of 2014 AD16 from the impact hazard assessment page (this was a newly discovered, Systematic Survey Night target). More than 90% of the time, Arecibo astrometry for discovery apparition cases leads to securing orbit knowledge well enough to predict the next Earth encounter, i.e, the astrometry prevents the object from being lost and requiring rediscovery at some future date. For first apparition objects, radar astrometry expands the window of Earth encounter predictability by about 5x on average; from 80 years (optical only) to about 400 years for solutions based on optical and radar astrometry (Ostro & Giorgini, 2004).

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Figure 4: (left) Initial CW spectra of 1994 CJ1 , obtained during a scheduled astrometry run, and showing the unusual double-spike of two, closely-orbiting objects. (right) A follow-up Delay-Doppler radar image of the 1994 CJ1 equal-mass binary system with coarse resolution of 75 m per pixel. While this binary did not come close enough to Earth for high-resolution imaging, it represents a unique and noteworthy find that would not have happened without regular monitoring of astrometry targets.

We propose to observe approximately 2/3 of the 39 astrometry objects listed in Table 4 with precedence given to PHAs and NHATS objects amounting to approximately 80 hours, including transmitter warm-up time. Multiple targets that can be done close in time or combined with monthly 8-hour survey nights are preferred. Objects unexpectedly bright and/or of particular interest will be observed on additional days if the schedule allows. We will work with the scheduler to find the most convenient method of scheduling the astrometry targets. While not having high predicted SNRs, astrometry targets can provide scientifically intriguing results. Asteroid 1994 CJ1 was observed as an astrometry target in summer 2014 and found to be only the second known equal-mass binary near-Earth asteroid, after (69230) Hermes, and possibly the smallest binary asteroid known with components less than 150 m in diameter. If not for the observing track scheduled for astrometry of this PHA and NHATS object, we would not have discovered its binary nature shown in Figure 4.

5 Systematic Survey Nights
In addition to the previously discovered asteroids that we propose to observe as either moderateresolution imaging targets (Sec. 3) or astrometry targets (Sec. 4), we propose to conduct an evening-long (8 hr) survey of available asteroids once every month, primarily focusing on newly discovered objects that are not predicted to be strong enough to warrant an urgent proposal request. In order to determine the best night of the month for such `new discovery survey nights', we conducted a statistical study of all asteroid discoveries and their subsequent observability at Arecibo Observatory for the years 2008 to 2014, and found that, generally speaking, the most favorable night for such new discovery surveys is around the time of new moon. The reason for this correlation with the new moon is as follows: 1. The period of full moon produces a gap of about 1.0­1.5 weeks in the discovery cadence at the asteroid survey sites (Catalina Sky Survey (CSS), Pan-STARRS, etc.), when these observatories are not active. 5


Figure 5: A plot of the total number of asteroids per day observable with the Arecibo Observatory planetary radar that are at a distance of less than 0.9 AU, such that the round trip time (RTT) is less than 15 minutes and the total transmit/receive cycle time is less than half an hour. The day of full moon is indicated in red. Note the general peaks that occur near the time of new moon, midway between the red lines, due to new asteroid discoveries becoming observable around that time. Zero values in the number of asteroids are due to compiled data dropouts, rather than an actual lack of targets.

2. The week immediately following this gap often contains a small bump in the number of new discoveries, as new objects that breached the discovery brightness threshold during the time of full moon are picked up in the subsequent week once the moon begins to dim again. 3. The average delay time between asteroid discovery and the object's initial, best visibility date at Arecibo Observatory is roughly 4 ± 3 days. 4. The above three items thus produce a broad peak in the number of new discoveries visible at Arecibo roughly centered around the time of new moon: see Figure 5 and Table 1. This survey request is nominally for one 8-hour run, about 20:00-4:00 AST, on the date of new moon ±3 days; that is, within the one-week window centered on the new moon. Table 2 lists the 13 new moon dates for the 2016 calendar year. To obtain radar astrometry, we require about 30-45 minutes per target, assuming average brightness, in order to get Doppler and ranging detections for asteroids up to a few minutes light travel time away. If the object is brighter, we will obtain images and determine the asteroid's general shape. If no detection is made after 20-30 minutes, we move on to the next target. Astrometry targets from Table 4 that are available at this time will be observed. This adds up to 117 hours for 2016, (including 1 hr of transmitter warmup time prior to each session), although some blocks may overlap with the moderate imaging targets.

6 Broader Impacts and Student Participation
Characterizing NEAs is a high priority if the current sample-return missions are to lead to a manned mission in the coming few decades. Public interest has been especially high lately due to the close pass of NEA 2012 DA14, and the fall of the Chelyabinsk meteorite, coincidentally 6


Year 2008 2009 2010 2011 2012 2013 2014 2008-2014

Mean Offset 11.08 16.69 17.42 12.75 15.54 13.42 17.75 14.84

Std Dev 5.92 7.50 6.86 8.27 4.65 5.06 6.08 6.87

Table 1: A determination of the best night for conducting survey observations of new asteroid discoveries, as a function of days after the full moon. The results correlate broadly with the day of new moon, which occurs 14.75 days after full.

9 Jan 2016 8 Feb 2016 8 Mar 2016 7 Apr 2016 6 May 2016 4 Jun 2016 4 Jul 2016 2 Aug 2016 1 Sep 2016 30 Sep 2016 30 Oct 2016 29 Nov 2016 29 Dec 2016
Table 2: Dates of new moon in 2016 around which the survey night should be scheduled.

on the same day. The impact hazard, while a low probability event, is a real possibility, and has serious consequences. A one kilometer asteroid would almost certainly destroy civilization, though probably not every person on Earth. Radar is a unique method for characterizing the NEA population for future missions or impact mitigation and its precise astrometry is invaluable for orbit refinement, projecting asteroid trajectories into the future, and determining future hazards to Earth. We involve students in observations whenever possible. During the summer of 2014, two Cornell students, one UCF student, and two REU students were involved in taking, reducing and analyzing radar data. In the last 13 years, 23 summer students (mostly undergraduates, two high school students) have been involved in radar observing projects at Arecibo. Of these, six students are now in graduate school in planetary science, and one is post-doctoral fellow and two have faculty positions. One is a writer for Astronomy Magazine. A former student is working at the Planetary Society. Many more students have participated in observations with visiting observers.

References
ґ ґ Bottke, Jr., W. F., Vokrouhlicky, D., Rubincam, D. P., Nesvorny, D., May 2006. The Yarkovsky and Yorp Effects: Implications for Asteroid Dynamics. Annual Review of Earth and Planetary Sciences 34, 157­191. Ostro, S. J., Giorgini, J. D., 2004. The role of radar in predicting and preventing asteroid and comet collisions with Earth. In: Belton, M. J. S., Morgan, T. H., Samarasinha, N. H., Yeomans, D. K. (Eds.), Mitigation of Hazardous Comets and Asteroids. p. 38. Warner, B. D., Harris, A. W., Pravec, P., Jul. 2009. The asteroid lightcurve database. Icarus 202, 134­146.

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Table 3: 2016 Moderate Imaging Targets
PHA Y Y Y Y 137805 Y Y Y 3103 250458 Y Y Y 96590 Y Y Y 418849 438955 406952 388945 NHATS Number H Mag. 2012 BU61 21.3 2000 BM19 18.3 2008 EP6 19.3 2014 EK24 23.3 1999 YK5 16.6 2010 FX9 24.2 2009 KJ 17.1 2008 TZ3 20.4 2014 US115 24.6 2002 LY1 22.1 Eger 15.4 2004 BO41 17.8 2009 ES 20.5 2014 UR 26.6 2004 KB 21.1 1998 XB 16.2 2007 VM184 21.0 2008 WM64 20.6 2010 LN14 21.1 Name Diam. (km) 0.122 0.485 0.306 0.048 1.060 0.032 0.842 0.184 0.027 0.084 1.859 0.610 0.176 0.011 0.133 1.275 0.140 0.168 0.133 Rotation Per. (hr) 9.47 0.0978 Start Date 6 Jan 2016 1 Jan 2016 8 Jan 2016 22 Feb 2016 26 Feb 2016 12 Mar 2016 25 Mar 2016 16 Apr 2016 26 Apr 2016 10 Jun 2016 14 Jul 2016 1 Sep 2016 10 Sep 2016 10 Oct 2016 9 Nov 2016 30 Nov 2016 23 Nov 2016 18 Dec 2016 11 Jan 2017 End Date 12 Jan 2016 15 Jan 2016 18 Jan 2016 3 Mar 2016 7 Mar 2016 30 Mar 2016 5 Apr 2016 26 Apr 2016 30 Apr 2016 22 Jun 2016 26 Jul 2016 12 Sep 2016 18 Sep 2016 18 Oct 2016 11 Nov 2016 10 Dec 2016 12 Dec 2016 22 Dec 2016 24 Jan 2017 Optimum Date 7 Jan 2016 12 Jan 2016 18 Jan 2016 24 Feb 2016 28 Feb 2016 22 Mar 2016 5 Apr 2016 26 Apr 2016 30 Apr 2016 13 Jun 2016 24 Jul 2016 7 Sep 2016 10 Sep 2016 18 Oct 2016 11 Nov 2016 1 Dec 2016 2 Dec 2016 21 Dec 2016 15 Jan 2017 Rise (UT) 4:00 11:45 15:30 2:15 16:45 2:00 16:45 5:15 19:45 22:00 8:30 17:45 1:15 8:00 13:45 2:15 22:30 7:45 9:00 S et (UT) 6:00 13:00 17:30 4:30 19:15 4:45 18:00 6:30 22:15 0:30 9:45 20:45 2:30 10:00 15:30 3:45 1:15 9:30 11:30 Track Range SNR per SNR per Note Dur. (hr) (AU) Scan Track 2.00 0.052 21.3 186.4 A 1.25 0.111 18.8 109.6 2.00 0.081 28.1 168.4 1.25 0.039 14.2 125.5 2.50 0.154 19.6 94.2 2.75 0.025 33.0 370.1 A 1.25 0.138 20.3 90.1 1.25 0.063 32.1 175.7 2.50 0.025 26.5 361.8 A 2.50 0.051 13.1 118.2 1.25 0.211 15.3 49.3 E 3.00 0.101 37.7 257.2 1.25 0.065 26.9 157.0 2.00 0.011 38.8 820.2 R 1.75 0.023 405.3 5830.8 A 1.50 0.160 23.0 82.9 RS 2.75 0.056 32.5 286.7 A 1.75 0.071 18.1 145.6 2.50 0.058 16.8 142.4

162385 438661

8

5.706

0.2 520

Table 3: Total track time = 74 hrs, given two tracks (days) per object. Assuming 1 hour of transmitter warmup time added, this totals 112 hrs of requested telescope time. Notes: A = optical astrometry needed prior to radar observations; E = spectral class E object with expected high polarization ratio; R = prior radar target; S = slowly rotationg asteroid such that SNR may be higher than predicted.


Table 4: 2016 Astrometry Targets
PHA NHATS Number Y Y Y Y Y Y Y 7822 7350 23187 20826 Name 2007 BB 2015 BN509 1999 VF22 2007 DS7 1991 CS 2008 DL5 1993 VA 2015 DR215 2000 PN9 2000 UV13 2005 GR33 2013 KJ6 2002 AJ29 2002 CX58 1997 XF11 2002 LT38 2011 BX18 2005 OH3 1997 WU22 Hansen Ra-Shalom 1998 SD15 2011 DU 2012 UA34 2012 JT17 2005 TF 1998 VN 2002 QF15 1998 MZ 2001 LL5 2000 EA107 2009 TB8 2005 WS3 2002 WP 2014 EW24 2012 YK Toutatis 2005 EE Atira H Diam. Mag. (km) 27.8 0.006 20.8 0.153 20.5 0.176 25.8 0.015 17.4 0.733 21.9 0.092 17.0 0.882 20.0 0.222 16.1 1.335 13.8 3.849 22.0 0.088 19.8 0.243 17.3 0.768 22.1 0.084 16.9 0.923 20.3 0.193 18.0 0.556 26.0 0.014 15.5 1.759 13.8 3.849 16.1 1.366 19.1 0.335 21.1 0.133 19.5 0.279 18.6 0.422 20.1 0.212 20.5 0.176 16.4 1.162 19.3 0.306 19.1 0.335 15.8 1.532 18.2 0.507 21.2 0.127 18.3 0.485 19.4 0.292 23.0 0.056 15.3 1.929 21.3 0.122 16.3 1.217 Rotation Per. (hr) Start Date 11 Jan 2016 25 Jan 2016 7 Feb 2016 23 Feb 2016 26 Feb 2016 3 Mar 2016 1 Mar 2016 14 Mar 2016 13 Mar 2016 23 Mar 2016 28 Mar 2016 17 Apr 2016 25 Apr 2016 3 May 2016 27 May 2016 23 Jun 2016 15 Jul 2016 15 Jul 2026 15 Jul 2016 30 Aug 2016 6 Sep 2016 18 Sep 2016 17 Sep 2016 16 Oct 2016 26 Oct 2016 2 Nov 2016 3 Nov 2016 5 Nov 2016 9 Nov 2016 21 Nov 2016 19 Nov 2016 25 Nov 2016 21 Nov 2016 27 Nov 2016 12 Dec 2016 15 Dec 2016 23 Dec 2016 16 Jan 2017 15 Jan 2017 End Date 25 Jan 2016 4 Feb 2016 17 Feb 2016 4 Mar 2016 7 Mar 2016 12 Mar 2016 11 Mar 2016 25 Mar 2016 22 Mar 2016 8 Apr 2016 7 Apr 2016 28 Apr 2016 7 May 2016 14 May 2016 16 Jun 2016 3 Jul 2016 9 Aug 2016 26 Jul 2016 8 Aug 2016 12 Sep 2016 17 Sep 2016 28 Sep 2016 26 Sep 2016 29 Oct 2016 5 Nov 2016 14 Nov 2016 14 Nov 2016 16 Nov 2016 23 Nov 2016 2 Dec 2016 5 Dec 2016 5 Dec 2016 2 Dec 2016 16 Dec 2016 24 Dec 2016 25 Dec 2016 8 Jan 2017 25 Jan 2017 25 Jan 2017 Optimum Date 19 Jan 2016 3 Feb 2016 16 Feb 2016 24 Feb 2016 28 Feb 2016 3 Mar 2016 10 Mar 2016 16 Mar 2016 17 Mar 2016 3 Apr 2016 7 Apr 2016 26 Apr 2016 28 Apr 2016 5 May 2016 7 Jun 2016 25 Jun 2016 25 Jul 2016 26 Jul 2016 27 Jul 2016 5 Sep 2016 16 Sep 2016 21 Sep 2016 23 Sep 2016 26 Oct 2016 27 Oct 2016 12 Nov 2016 13 Nov 2016 15 Nov 2016 20 Nov 2016 23 Nov 2016 26 Nov 2016 27 Nov 2016 1 Dec 2016 7 Dec 2016 22 Dec 2016 24 Dec 2016 29 Dec 2016 16 Jan 2017 18 Jan 2017 Rise (UT) 21:15 9:30 10:00 7:45 1:45 1:15 19:15 21:00 20:00 19:30 7:45 13:45 7:15 5:00 19:30 23:15 11:00 1:00 20:30 4:00 7:00 23:45 15:30 17:30 1:30 3:30 7:15 18:45 10:00 13:45 13:45 12:00 5:15 2:45 16:15 8:15 21:45 10:00 14:45 S et (UT) 0:15 10:45 11:15 9:00 4:15 3:00 21:00 22:30 23:15 21:45 9:30 16:30 9:00 8:00 22:15 1:30 14:00 2:15 23:15 6:00 8:30 2:45 16:15 20:00 2:30 5:00 9:15 20:45 12:30 16:15 16:45 14:30 7:15 5:45 18:30 10:30 0:00 12:00 17:15 Track Dur. (hr) 3.00 1.25 1.25 1.25 2.50 1.75 1.75 1.50 3.25 2.25 1.75 2.75 1.75 3.00 2.75 2.25 3.00 1.25 1.75 2.00 1.50 3.00 0.75 2.50 1.00 1.50 2.00 2.00 2.50 2.50 3.00 2.50 2.00 3.00 2.25 2.25 2.25 2.00 2.50 Range SNR per SNR per Note (AU) Scan Track 0.015 5.7 101.0 A 0.085 8.5 34.3 A 0.098 6.4 24.8 0.019 9.4 71.1 A 0.177 7.0 33.0 R 0.063 7.1 44.5 0.183 8.2 32.5 0.106 6.4 25.9 0.234 6.5 29.0 R 0.339 8.7 31.2 0.051 14.0 82.3 0.096 11.1 74.7 0.177 7.5 27.9 0.056 9.3 77.2 A 0.180 9.3 45.4 R 0.078 16.4 98.4 0.138 10.9 63.6 A 0.021 6.7 77.8 A 0.249 7.9 31.6 R 0.310 11.9 41.1 0.232 6.9 21.1 R 0.123 7.7 46.2 0.064 11.9 35.8 0.096 13.6 86.8 0.121 11.4 53.5 0.104 7.0 37.0 A 0.090 8.5 52.7 0.166 17.3 83.1 RS 0.107 10.8 68.0 0.114 10.0 56.2 0.249 6.5 27.9 0.136 10.1 52.8 0.074 6.6 44.7 0.153 6.3 35.1 0.116 7.6 44.8 A 0.053 5.9 42.9 0.251 8.8 34.0 RS 0.068 8.5 38.1 0.210 8.3 26.6

2.389

2.53 12

141354 Y Y Y Y 35396 Y Y 16834 4775 2100 162117 Y Y

3.259

9.345 19.797

9
Y Y Y Y Y

326302 68950 152685 162911 152931

47

4.137

326683

4179 265482 163693

176 2.9745

Table 4: Total track time = 83 hrs, and with 1 hour of transmitter warmup time added, this totals 122 hrs of telescope time. We request to observe about 2/3 of these objects (about 80 hrs), with NHATS objects and PHAs having the highest priority. Notes: A = optical astrometry needed prior to radar observations; R = prior radar target; S = slowly rotating asteroid such that SNR may be higher than predicted.