J. D. Giorgini's research while affiliated with California Institute of Technology and other places

Publications (276)

Article
We conducted radar observations of near-Earth asteroid 2019 OK on 2019 July 25 using the Arecibo Observatory S-band (2380 MHz, 12.6 cm) planetary radar system. Based on Arecibo and optical observations the apparent diameter is between 70 and 130 m. Combined with an absolute magnitude of H = 23.3 ± 0.3, the optical albedo of 2019 OK is likely betwee...
Article
Ground-based planetary radar observations first revealed deposits of potentially nearly pure water ice in some permanently shadowed regions (PSRs) on Mercury’s poles. Later, the MESSENGER spacecraft confirmed the icy nature of the deposits, as well as their location within PSRs. Considering the geologic context provided by MESSENGER, we further cha...
Article
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We report observations of the Apollo-class potentially hazardous asteroid 1981 Midas, which passed 0.090 au from Earth (35 lunar distances) on 2018 March 21. During this close approach, Midas was observed by radar both from the Arecibo Observatory on March 21 through 25 (five nights) and from NASA’s Goldstone Deep Space Communications Complex on Ma...
Article
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Fundamental properties of the planet Venus, such as its internal mass distribution and variations in length of day, have remained unknown. We used Earth-based observations of radar speckles tied to the rotation of Venus obtained in 2006–2020 to measure its spin axis orientation, spin precession rate, moment of inertia and length-of-day variations....
Conference Paper
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Precise orbit determination is very important for planetary defense against Potentially Hazardous Asteroids (PHAs), to determine their probability of impact at close approaches to Earth as far as possible into the future. Orbits of NEOs are generally best improved by radar observations, but these are only possible when the NEO is relatively close t...
Preprint
Fundamental properties of the planet Venus, such as its internal mass distribution and variations in length of day, have remained unknown. We used Earth-based observations of radar speckles tied to the rotation of Venus obtained in 2006-2020 to measure its spin axis orientation, spin precession rate, moment of inertia, and length-of-day variations....
Article
We report results of Canberra-ATCA Doppler-only continuous wave (CW) radar observations of near-Earth asteroid (163899) 2003 SD220 at a receiving frequency of 7159 MHz (4.19 cm) on 2018 December 20, 21, and 22 during its close approach within 0.019 au (7.4 lunar distances). Echo power spectra provide evidence that the shape is significantly elongat...
Preprint
Full-text available
We report results of Canberra-ATCA Doppler-only continuous wave (CW) radar observations of near-Earth asteroid (163899) 2003 SD220 at a receiving frequency of 7159 MHz (4.19 cm) on 2018 December 20, 21, and 22 during its close approach within 0.019 au (7.4 lunar distances). Echo power spectra provide evidence that the shape is significantly elongat...
Article
Near-Earth asteroid Didymos is a binary system and the target of the proposed Double Asteroid Redirection Test (DART) mission (Cheng et al., 2016), which is a planetary defense experiment. The DART spacecraft will impact the satellite, causing changes in the binary orbit that would be measured by Earth-based observers. We observed Didymos using the...
Presentation
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The presentation is about the successful predictions and observational campaigns to observe occultations of stars by (3200) Phaethon, an active asteroid that is the parent body of the Geminids meteors. A shorter version of this was given as a poster at the "Asteroid Science in the Age of Hayabusa 2 and OSIRIS-REx" workshop held in Tucson, Arizona i...
Preprint
Full-text available
Planetary radars have obtained unique science measurements about solar system bodies and they have provided orbit determinations allowing spacecraft to be navigated throughout the solar system. Notable results have been on Venus, Earth's "twin," and small bodies, which are the constituents of the Sun's debris disk. Together, these results have serv...
Article
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The B-plane is a fundamental tool to analyze planetary encounters of small bodies and spacecraft flybys. In this paper, we review the B-plane formulation with a full derivation of its coordinates and their partial derivatives, which allow the mapping of orbital uncertainties onto the B-plane. We find that this mapping can be sensitive to variations...
Article
We measured the length of the Venus sidereal day (LOD) from Earth-based radar observations collected from 1988 to 2017, using offsets in surface feature longitudes from a prediction based on a 243.0185d period derived from analysis of Magellan mission images over a 487-day interval. We derive a mean LOD over 29 years of 243.0212 ± 0.0006d. Our resu...
Conference Paper
Full-text available
Introduction: To date, only four equal-mass binary asteroids have been discovered among the near-Earth population: (69230) Hermes, 1994 CJ1, (190166) 2005 UP156, and 2017 YE5, all of which have been characterized with radar and optical lightcurves. Equal-mass binaries are relatively rare, making up less than 1% of radar-observed near-Earth objects...
Article
Full-text available
We report Arecibo S-band (2380 MHz; 12.6 cm) radar observations of near-Earth asteroid (3200) Phaethon during the December 2017 apparition when Phaethon passed within 0.07 au of Earth. Radar images with a resolution of 75 m per pixel reveal a roughly spheroidal shape more than 6 km in diameter at the equator with several discernible surface feature...
Article
Impacts due to near-Earth objects (NEOs) are responsible for causing some of the great mass extinctions on Earth. While nearly all NEOs of diameter > 1 km, capable of causing a global climatic disaster, have been discovered and have negligible chance of impacting in the near future, we are far from completion in our effort to detect and characteriz...
Article
We report radar observations of near-Earth asteroid 2013 BS45 obtained during the 2013 apparition. This object is in a resonant, Earth-like orbit, and it is a backup target for NASA's NEA Scout mission. 2013 BS45 belongs to the Arjuna orbital domain, which currently has ∼20 discovered representatives. These objects tend to be small and difficult to...
Article
Full-text available
1I/`Oumuamua is the first confirmed interstellar body in our Solar System. Here we report on observations of `Oumuamua made with the Spitzer Space Telescope on 2017 November 21--22 (UT). We integrated for 30.2~hours at 4.5 micron (IRAC channel 2). We did not detect the object and place an upper limit on the flux of 0.3 uJy (3sigma). This implies an...
Article
We used three different sets of Arecibo delay-Doppler radar images and five well-covered occultations to generate a revised three-dimensional shape model of asteroid (216) Kleopatra with a spatial resolution of ∼10 km. We find Kleopatra to be a bi-lobate contact binary of overall dimensions 276 × 94 × 78 km ± 15% and equivalent diameter Deq = 122 ±...
Conference Paper
Full-text available
We observed Phaethon with the Arecibo planetary radar system from 2017 December 15 to 19 obtaining range-Doppler images with complete rotational coverage at a resolution of 75 meters per pixel and used the Goldstone Solar System Radar to collect echo power spectra of Phaethon almost daily from December 11 to 21.
Article
We describe the first demonstration of a southern hemisphere planetary radar system to detect two near-Earth asteroids (NEAs). The demonstration was conducted in a bistatic manner, with the 70 m antenna of the Canberra Deep Space Communications Complex transmitting at 2.1 GHz and reception at the Parkes Radio Telescope, outfitted with multiple rece...
Article
We report radar observations of Apophis obtained during the 2012−2013 apparition. We observed Apophis on fourteen days at Goldstone (8560 MHz, 3.5 cm) and on five days at Arecibo (2380 MHz, 12.3 cm) between 2012 December 21 to 2013 March 16. Closest approach occurred on January 9 at a distance of 0.097 au. We obtained relatively weak echo power spe...
Article
We report radar observations of near-Earth asteroid (469896) 2005 WC1 that were obtained at Arecibo (2380 MHz, 13 cm) and Goldstone (8560 MHz, 3.5 cm) on 2005 December 14–15 during the asteroid's approach within 0.020 au The asteroid was a strong radar target. Delay-Doppler images with resolutions as fine as 15 m/pixel were obtained with 2 samples...
Article
We report radar and optical photometric observations of near-Earth asteroid (214869) 2007 PA8 obtained during October 2-November 13, 2012. We observed 2007 PA8 on sixteen days with Goldstone (8560MHz, 3.5cm) and on five days with the 0.6m telescope at Table Mountain Observatory. Closest approach was on November 5 at a distance of 0.043au. Images ob...
Article
Using the S-band radar at Arecibo Observatory, we observed 16 Psyche, the largest M-class asteroid in the main belt. We obtained 18 radar imaging and 6 continuous wave runs in November and December 2015, and combined these with 16 continuous wave runs from 2005 and 6 recent adaptive-optics (AO) images (Drummond et al., 2016) to generate a three-dim...
Article
Comets rarely come close enough to be studied intensively with Earth-based radar. The most recent such occurrence was when Comet 103P/Hartley 2 passed within 0.12 AU in late 2010 October, less than two weeks before the EPOXI flyby. This offered a unique opportunity to improve pre-encounter trajectory knowledge and obtain complementary physical data...
Article
Radar instruments play a critical role in studies of Near-Earth Asteroids (NEAs) on two distinct levels: trajectory prediction and physical characterization.
Article
Radar observations are a powerful technique to study near-Earth asteroids (NEAs). Goldstone's 3.75 m resolution capability is invaluable when attempting to image NEAs with diameters smaller than 140 m. The small NEAs are a very diverse population in which we continue to discover unusual objects.
Article
The Mars flyby of C/2013 A1 (Siding Spring) represented a unique opportunity for imaging a long-period comet and resolving its nucleus and rotation period. Because of the small encounter distance and the high relative velocity, the goal of successfully observing C/2013 A1 from the Mars orbiting spacecrafts posed strict accuracy requirements on the...
Article
In 1978, the 3rd International Sun–Earth Explorer (ISEE-3) became the first libration-point mission, about the Sun–Earth L1 point. Four years later, a complex series of lunar swingbys and small propulsive maneuvers ejected ISEE-3 from the Earth–Moon system, to fly by a comet (Giacobini–Zinner) for the first time in 1985, as the rechristened Interna...
Article
Potentially hazardous asteroid (185851) 2000 DP107 was the first binary near-Earth asteroid to be imaged. Radar observations in 2000 provided images at 75 m resolution that revealed the shape, orbit, and spin-up formation mechanism of the binary. The asteroid made a more favorable flyby of the Earth in 2008, yielding images at 30 m resolution. We u...
Article
Full-text available
We have carried out simulations to predict the performance of a new space-based telescopic survey operating at thermal infrared wavelengths that seeks to discover and characterize a large fraction of the potentially hazardous near-Earth asteroid (NEA) population. Two potential architectures for the survey were considered: one located at the Earth-S...
Article
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Using the S-band radar at Arecibo Observatory, we observed thirteen X/M-class asteroids; nine were previously undetected and four were re-observed, bringing the total number of Tholen X/M-class asteroids observed with radar to 29. Of these 29M-class asteroids, 13 are also W-class, defined as M-class objects that also display a 3-μm absorption featu...
Chapter
Radar is a very powerful technique for characterizing near-Earth and main-belt asteroids and for improving their orbits. This results from radar’s ability to spatially resolve objects that often cannot be resolved at comparable resolutions by other groundbased techniques. Radar has revealed binary and contact binary objects, at least two triple sys...
Article
Arecibo (2380 MHz, 12.6 cm) and Goldstone (8560 MHz, 3.5 cm) radar observations between 2012 July 12 and August 8 revealed that Apollo-class and potentially hazardous asteroid (153958) 2002 AM31 is a binary system. It is comprised of a primary component 400-500 meters in diameter and a possibly asynchronous secondary about one-fourth that size. The...
Article
Using the S-band radar at Arecibo Observatory, we have observed 27 main-belt M-class asteroids, including 12 which display a 3 micron absorption feature often attributed to the presence of hydrated minerals (Rivkin et al, Icarus 145, 2000). Five of these “W-class” objects - 40% of our sample - have a mean radar albedo of 0.39 which is usually inter...
Article
We present the three-dimensional shape of near-Earth asteroid (101955) Bennu (provisional designation 1999 RQ36) based on radar images and optical lightcurves (Nolan et al., 2013). Bennu was observed both in 1999 at its discovery apparition, and in 2005 using the 12.6-cm radar at the Arecibo Observatory and the 3.5-cm radar at the Goldstone trackin...
Article
We determine the three-dimensional shape of near-Earth Asteroid (101955) Bennu based on radar images and optical lightcurves. Bennu was observed both in 1999 at its discovery apparition, and in 2005 using the 12.6-cm radar at the Arecibo Observatory and the 3.5-cm radar at the Goldstone tracking station. Data obtained in both apparitions were used...
Article
We report Goldstone radar (8560 MHz, 3.5 cm) observations of potentially hazardous asteroid (214869) 2007 PA8. 2007 PA8 approached within 0.043 AU (17 lunar distances) on November 5, 2012 when it was the target of an extensive radar observing campaign. Goldstone's new chirp system imaged the asteroid with 3.75 m range resolution and placed thousand...
Article
Full-text available
We observed near-Earth asteroid (162421) 2000 ET70 using the Arecibo and Goldstone radar systems over a period of 12 days during its close approach to the Earth in February 2012. We obtained continuous wave spectra and range-Doppler images with range resolutions as fine as 15 m. Inversion of the radar images yields a detailed shape model with an ef...
Article
Near-Earth asteroid 341843 (2008 EV5) was discovered on 2008 March 4 by the Catalina Sky Survey, and observed extensively during and after an 8.4 lunar distance (0.022 AU) Earth approach on 2008 December 23. EV5 is particularly accessible and has been selected as the primary target of ESA's proposed MarcoPolo-R sample-return mission. MarcoPolo-R is...
Article
We report delay-Doppler radar images of 2003 MS2 that were obtained at Goldstone (8560 MHz, 3.5 cm) on three dates during this object’s close Earth flyby in July of 2003 within 0.025 AU (9.7 lunar distances). The asteroid was a strong radar target and we obtained images with resolutions as high as 19 m/pixel. The radar images reveal an unusually an...
Article
Full-text available
Earth-based radar observations of the spin state of Mercury at 35 epochs between 2002 and 2012 reveal that its spin axis is tilted by (2.04 ± 0.08) arc min with respect to the orbit normal. The direction of the tilt suggests that Mercury is in or near a Cassini state. Observed rotation rate variations clearly exhibit an 88-day libration pattern whi...
Article
We used planetary radar images and visible lightcurves of asteroid (101955) 1999 RQ36 obtained in 1999 and 2005 to create a three-dimensional shape model of the asteroid and to constrain its surface properties. Radar images at 19-, 15- and 7.5-m resolution taken with the Arecibo and Goldstone planetary radar systems in September/October 1999 and Se...
Article
We report Arecibo (2380 MHz), 13-cm) and Goldstone (8560 MHz, 3.5-cm) delay-Doppler radar observations of binary near-Earth asteroid and Marco Polo-R mission target (175706) 1996 FG3 that were obtained on nine dates between November 6-December 17, 2011. The images achieve resolutions as fine as 75 m in range and place hundreds of pixels on the prim...
Article
At least 10% of near-Earth asteroids larger than 200 m in diameter observed by radar are contact binaries, which we define as objects composed of two lobes in contact with each other that may once have been in mutual orbit. We will present new shape models and pole directions for three contact binaries imaged by radar: 11066 Sigurd, 2000 YF29, and...
Article
Asteroid 2000 ET70 was discovered by the LINEAR program on Mar 8th, 2000. During its close approach to the Earth in Feb 2012 ( 0.045 A.U), we acquired 350 range-Doppler images over 6 days with range resolutions as fine as 15 meters using the Arecibo Planetary Radar (2380 MHz, 13 cm). We also obtained 800 range-Doppler images over 9 days with range...
Article
Several space missions to Near Earth Asteroids (NEAs) are being planned over the coming decades. Robust mission design and risk management both require ground-based radar reconnaissance of target NEAs (e.g. precise trajectories, presence of satellites, sizes, shapes, spins). However the number of potential targets that have both low delta-V and hig...
Article
We present the preliminary results of an analysis of the sub-populations within the near-Earth asteroids, including the Atens, Apollos, Amors, and those that are considered potentially hazardous using data from the Wide-field Infrared Survey Explorer (WISE). In order to extrapolate the sample of objects detected by WISE to the greater population, w...
Article
On 2011 November 8, 2005 YU55 made a 0.845 lunar distance flyby. We organized a radar campaign using Arecibo, Goldstone, the GBT, and the VLBA. YU55 is 360 ± 40 m in diameter, has a surface strewn with 10-m scale boulders, and spins retrograde.
Article
Full-text available
JPL's NEO Program Office website (neo.jpl.nasa.gov) has added an on-line tool for information on viable human NEA missions and another educational tool whereby users can design spacecraft-NEA impact missions to deflect hypothetical Earth impactors.
Article
Near-Earth Asteroid (35107) 1991 VH was discovered to be a binary in March 1997, based on its light-curve (IAUC 6607). It made a very close approach to the Earth in August 2008 at a distance of 0.045 AU. We used this opportunity to secure an extensive radar data set with the Arecibo S-band (2380 MHz, 13 cm wavelength) planetary radar system, includ...
Article
We present shape modeling of near-Earth asteroid (53319) 1999 JM8 based on Arecibo (S-band, 2380 MHz) and Goldstone (X-band, 8560 MHz) data obtained from July 18-Aug. 8, 1999. Our preliminary results suggest that 1999 JM8 is a long-axis NPA rotator.
Article
101955 (1999 RQ36) is a 500-m diameter Potentially Hazardous Asteroid and the target of the OSIRIS-REx sample return mission. September 2011 radar ranging from the Arecibo Observatory to 1999 RQ36 unambiguously reveals the action of the Yarkovsky effect, which manifests as a mean semimajor axis drift, da/dt = -18.99±0.10 ×10-4 AU/My. Here da/dt is...
Article
Using the Arecibo radar, we observed seven new X/M-class MBAs. We find 40% of 26 total observed have metal-like radar albedos. Four W-class (hydrated M's) have metal-like radar albedos. Forty percent of X/M MBAs show evidence of bifurcation.
Article
Arecibo S-band (2380-MHz, 13-cm) radar observations in April 2010 determined that near-Earth asteroid 2005 YU55 is a dark, spherical object about 400 meters in diameter with a slow rotation period of roughly 18 hours. Radar astrometry provided by Arecibo during the 2010 apparition substantially improved the orbit of 2005 YU55, eliminating it as a p...
Article
We report radar, photometric, and spectroscopic observations of near-Earth Asteroid (136617) 1994 CC. The radar measurements were obtained at Goldstone (8560MHz, 3.5cm) and Arecibo (2380MHz, 12.6cm) on 9days following the asteroid’s approach within 0.0168AU on June 10, 2009. 1994 CC was also observed with the Panchromatic Robotic Optical Monitoring...
Article
2000 DP107 was the first Near Earth Asteroid (NEA) binary ever imaged [1]. During its 2008 return, the radar signal-to-noise ratio was 20 times higher than in 2000, which provided an opportunity to obtain very detailed images with range resolution as fine as 30 m. The 2008 observability window spanned 16 days, allowing for excellent rotational and...
Article
In 2004, Toutatis passed within 0.0104 AU of Earth. The method of Scheeres et al. 2000 [4] predicts that tidal torques during that flyby should have significantly changed Toutatis' spin state due to its elongated shape and slow rotation. We have analyzed all of the available radar data, developing an improved model of Toutatis' rotation. Between 20...
Article
We report new radar observations of E-class Asteroid 64 Angelina and M-class Asteroid 69 Hesperia obtained with the Arecibo Observatory S-band radar (2480MHz, 12.6cm). Our measurements of Angelina’s radar bandwidth are consistent with reported diameters and poles. We find Angelina’s circular polarization ratio to be 0.8±0.1, tied with 434 Hungaria...
Article
We observed near-Earth Asteroid (8567) 1996 HW1 at the Arecibo Observatory on six dates in September 2008, obtaining radar images and spectra. By combining these data with an extensive set of new lightcurves taken during 2008–2009 and with previously published lightcurves from 2005, we were able to reconstruct the object’s shape and spin state. 199...
Article
Arecibo radar observations of Comet Hartley from October 25-31, 2010, provide data complementing the EPOXI flyby, including spin state (period, pole, etc.), surface density, and large-grain production.
Article
The flexible path is one of several space exploration strategy options developed by the Review of U.S. Human Space Flight Plans Committee in 2009. Among proposed flexible path destinations are near-Earth objects, those asteroids and comets having perihelions of less than 1.3 astronomical units and periods of less than 200 years. Heliocentric-orbit...
Article
CBET 2515 available at Central Bureau for Astronomical Telegrams.
Article
We observed the near-Earth binary system 2000 CO101 in 2009 September using the Goldstone and Arecibo radar systems and inverted these images to create shape models of the primary. Asteroid 2000 CO101 was discovered to be a binary system from Arecibo images taken on 2009 September 26 (Taylor et al. 2009). Analyzing the images, we were able to deter...
Article
Knowing the shapes and spin states of near-Earth asteroids is essential to understanding their dynamical evolution because of the Yarkovsky and YORP effects. Delay-Doppler radar imaging is the most powerful ground-based technique for imaging near-Earth asteroids and can obtain spatial resolution of <10 m, but frequently produces ambiguous pole dire...
Article
The near-Earth asteroid 2008 EV5 was discovered by the Mt. Lemmon Survey on March 4 2008, and approached to within 8.4 lunar distances in December 2008, when it was a very strong radar target. We observed EV5 with the Arecibo and Goldstone planetary radars and the Very Long Baseline Array, and previously described those observations and obtaining E...