Andrew Cheng

Johns Hopkins University | JHU · Applied Physics Laboratory

The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on September 26, 2022 as a planetary defense test. DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defense,...

The Double Asteroid Redirection Test (DART) spacecraft successfully performed the first test of a kinetic impactor for asteroid deflection by impacting Dimorphos, the secondary of near-Earth binary asteroid (65803) Didymos, and changing the orbital period of Dimorphos. A change in orbital period of approximately 7 minutes was expected if the incide...

While no known asteroid poses a threat to Earth for at least the next century, the catalog of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation. Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid. A test of kinetic impact te...

Some active asteroids have been proposed to be the result of impact events. Because active asteroids are generally discovered serendipitously only after their tail formation, the process of the impact ejecta evolving into a tail has never been directly observed. NASA's Double Asteroid Redirection Test (DART) mission, apart from having successfully...

The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on September 26, 2022 as a planetary defense test1. DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defense,...

The Double Asteroid Redirection Test (DART) spacecraft successfully performed the first test of a kinetic impactor for asteroid deflection by impacting Dimorphos, the secondary of near-Earth binary asteroid (65803) Didymos, and changing the orbital period of Dimorphos. A change in orbital period of approximately 7 minutes was expected if the incide...

While no known asteroid poses a threat to Earth for at least the next century, the catalog of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation1,2. Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid1-3. A test of kinetic imp...

Some active asteroids have been proposed to be the result of impact events1. Because active asteroids are generally discovered serendipitously only after their tail formation, the process of the impact ejecta evolving into a tail has never been directly observed. NASA's Double Asteroid Redirection Test (DART) mission2, apart from having successfull...

NASA’s Double Asteroid Redirection Test (DART) mission intentionally impacted the asteroid Dimorphos on September 26, 2022, and this kinetic impact changed Dimorphos’ orbit around its binary companion Didymos. This first planetary defense test explored technological readiness for this method of asteroid deflection.

The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on September 26, 2022 as a planetary defense test ¹ . DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defens...

NASA’s Double Asteroid Redirection Test (DART) mission performed the first ever kinetic impact to deflect an asteroid ¹ . The DART kinetic impact test artificially activated an asteroid with a hypervelocity impact, providing a unique opportunity for an extensive observing campaign to monitor the evolutionary process from the formation of the ejecta...

NASA's Double Asteroid Redirection Test (DART) is the first full-scale test of an asteroid deflection technology. Results from the hypervelocity kinetic impact and Earth-based observations, coupled with LICIACube and the later Hera mission, will result in measurement of the momentum transfer efficiency accurate to ∼10% and characterization of the D...

NASA's Double Asteroid Redirection Test (DART) is the first full-scale test of an asteroid deflection technology. Results from the hypervelocity kinetic impact and Earth-based observations, coupled with LICIACube and the later Hera mission, will result in measurement of the momentum transfer efficiency accurate to ~10% and characterization of the D...

On 2022 September 26, the DART spacecraft will impact the surface of Dimorphos, the ∼160 m size satellite of the binary near-Earth asteroid (NEA) (65803) Didymos. What will be observed on the surfaces of both asteroids and at the DART impact site is largely unknown, beyond the details of Didymos revealed by previous Arecibo and Goldstone radar obse...

We overview various efforts within the DART Investigation Team’s Ejecta Working Group to predict the characteristics, quantity, dynamical behavior, and observability of DART impact ejecta. We discuss various methodologies for simulation of the impact/cratering process with their advantages and drawbacks in relation to initializing ejecta for subseq...

NASA's Double Asteroid Redirection Test (DART) spacecraft is planned to impact the natural satellite of (65803) Didymos, Dimorphos, around 23:14 UTC on 26 September 2022, causing a reduction in its orbital period that will be measurable with ground-based observations. This test of kinetic impactor technology will provide the first estimate of the m...

The Double Asteroid Redirection Test (DART) spacecraft will impact the moon Dimorphos of the [65803] Didymos binary in order to demonstrate asteroid deflection by a kinetic impactor. DART will measure the deflection by using ground-based telescopic observations of the orbital period change of Didymos and will carry the Light Italian CubeSat for Ima...

We present new, ice species-specific New Horizons/Alice upper gas coma production limits from the 2019 January 1 MU69/Arrokoth flyby of Gladstone et al. and use them to make predictions about the rarity of majority hypervolatile (CO, N 2 , CH 4 ) ices in Kuiper Belt objects and Oort Cloud comets. These predictions have a number of important implica...

We present new, ice species-specific New Horizons/Alice upper gas coma production limits from the 01 Jan 2019 MU69/Arrokoth flyby of Gladstone et al. (2021) and use them to make predictions about the rarity of majority hypervolatile (CO, N$_2$, CH$_4$) ices in KBOs and Oort Cloud comets. These predictions have a number of important implications for...

We used New Horizons LORRI images to measure the optical-band (0.4 ≲ λ ≲ 0.9 μ m) sky brightness within a high-galactic-latitude field selected to have reduced diffuse scattered light from the Milky Way galaxy (DGL), as inferred from the IRIS all-sky 100 μ m map. We also selected the field to significantly reduce the scattered light from bright sta...

We used New Horizons LORRI images to measure the optical-band ($0.4\lesssim\lambda\lesssim0.9{\rm\mu m}$) sky brightness within a high galactic-latitude field selected to have reduced diffuse scattered light from the Milky Way galaxy (DGL), as inferred from the IRIS all-sky $100~\mu$m map. We also selected the field to significantly reduce the scat...

We present a study of the current state of knowledge concerning spacecraft operations and potential hazards while operating near a comet nucleus. Starting from simple calculations comparing the cometary coma environment to benign conditions on Earth, we progress to sophisticated engineering models of spacecraft behavior, and then confront these mod...

Pluto, Titan, and Triton make up a unique class of solar system bodies, with icy surfaces and chemically reducing atmospheres rich in organic photochemistry and haze formation. Hazes play important roles in these atmospheres, with physical and chemical processes highly dependent on particle sizes, but the haze size distribution in reducing atmosphe...

NASA’s Lucy mission is the first to provide flyby reconnaissance of the Jovian trojan asteroids, which are thought to be primordial small bodies that formed at a variety of heliocentric distances during the early stages of the solar system’s formation and were subsequently captured into Jupiter’s L4 and L5 Lagrange stability zones. Since its succes...

The NASA Double Asteroid Redirection Test (DART) mission is a planetary defense-driven test of a kinetic impactor on Dimorphos, the satellite of the binary asteroid 65803 Didymos. DART will intercept Dimorphos at a relative speed of ∼6.5km s−1, perturbing Dimorphos’s orbital velocity and changing the binary orbital period. We present three independ...

We present a study of the current state of knowledge concerning spacecraft operations and potential hazards while operating near a comet nucleus. Starting from some simple back of the envelope calculations comparing the cometary coma environment to benign conditions on Earth, we progress to sophisticated engineering models of spacecraft behavior, a...

The Double Asteroid Redirection Test (DART) is a Planetary Defense mission, designed to demonstrate the kinetic impactor technique on (65803) Didymos I Dimorphos, the secondary of the (65803) Didymos system. DART has four level 1 requirements to meet in order to declare mission success: (1) impact Dimorphos between 2022 September 25 and October 2,...

The NASA Double Asteroid Redirection Test (DART) mission is a planetary defense-driven test of a kinetic impactor on Dimorphos, the satellite of the binary asteroid 65803 Didymos. DART will intercept Dimorphos at a relative speed of ${\sim}6.5 \text{ km s}^{-1}$, perturbing Dimorphos's orbital velocity and changing the binary orbital period. We pre...

Pluto, Titan, and Triton make up a unique class of solar system bodies, with icy surfaces and chemically reducing atmospheres rich in organic photochemistry and haze formation. Hazes play important roles in these atmospheres, with physical and chemical processes highly dependent on particle sizes, but the haze size distribution in reducing atmosphe...

Pluto, Titan and Triton all have low-temperature environments with an N2, CH4 and CO atmospheric composition in which solar radiation drives an intense organic photochemistry. Titan is rich in atmospheric hazes, and Cassini–Huygens observations showed that their formation is initiated with the production of large molecules through ion-neutral react...

We used existing data from the New Horizons Long-range Reconnaissance Imager (LORRI) to measure the optical-band (0.4 ≲ λ ≲ 0.9 μ m) sky brightness within seven high–Galactic latitude fields. The average raw level measured while New Horizons was 42–45 au from the Sun is 33.2 ± 0.5 nW m ⁻² sr ⁻¹ . This is ∼10× as dark as the darkest sky accessible t...

We used existing data from the New Horizons LORRI camera to measure the optical-band ($0.4\lesssim\lambda\lesssim0.9{\rm\mu m}$) sky brightness within seven high galactic latitude fields. The average raw level measured while New Horizons was 42 to 45 AU from the Sun is $33.2\pm0.5{\rm ~nW ~m^{-2} ~sr^{-1}}.$ This is $\sim10\times$ darker than the d...

We discuss in a thermodynamic, geologically empirical way the long-term nature of the stable majority ices that could be present in Kuiper Belt Object 2014 MU69 after its 4.6 Gyr residence in the EKB as a cold classical object. Considering the stability versus sublimation into vacuum for the suite of ices commonly found on comets, Centaurs, and KBO...

In this paper we discuss in a thermodynamic, geologically empirical way the long-term nature of the stable majority ices that could be present in Kuiper Belt object (KBO) 2014 MU69 (aka Arrokoth; hereafter “MU69”) after its 4.6 Gyr residence in the Edgeworth-Kuiper belt (EKB) as a cold classical object. We compare the upper bounds for the gas produ...

The NASA Double Asteroid Redirection Test (DART) spacecraft will impact the secondary member of the [65803] Didymos binary in order to perform the first demonstration of asteroid deflection by kinetic impact. Determination of the momentum transfer to the target body from the kinetic impact is a primary planetary defense objective, using ground-base...

The New Horizons mission has returned stunning images of the bilobate Kuiper belt object (486958) Arrokoth. It is a contact binary, formed from two intact and relatively undisturbed predecessor objects joined by a narrow contact region. We use a version of pkdgrav, an N-body code that allows for soft-sphere collisions between particles, to model a...

Observations during the New Horizons (NH) spacecraft flyby of Pluto in July 2015 revealed that Pluto's atmosphere supports an extensive circumplanetary haze with embedded layers, suggesting several possible microphysical and/or dynamical excitation processes. The purpose of this paper is to build upon existing observations and analyses of Pluto's a...

The New Horizons mission has returned stunning images of the bilobate Kuiper belt object (486958) Arrokoth. It is a contact binary, formed from two intact and relatively undisturbed predecessor objects joined by a narrow contact region. We use a version of pkdgrav, an N-body code that allows for soft-sphere collisions between particles, to model a...

NASA's Double Asteroid Redirection Test (DART) is designed to be the first demonstration of a kinetic impactor for planetary defense against a small-body impact hazard. The target is the smaller component of the binary asteroid 65,803 Didymos. We have conducted high-fidelity rigid full two-body simulations of the mutual dynamics of this system in a...

The Kuiper Belt is a distant region of the Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a Cold Classical Kuiper Belt Object, a class of objects that have never been heated by the Sun and are therefore well preserved since their formation. Here we describe initial results from these encounter observa...

The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, are primitive objects preserving information about Solar System formation. The New Horizons spacecraft flew past one of these objects, the 36 km long contact binary (486958) Arrokoth (2014 MU69), in January 2019. Images from the flyby show that Arrokoth ha...

On January 1st 2019, the New Horizons spacecraft flew by the classical Kuiper belt object (486958) Arrokoth (provisionally designated 2014 MU69), possibly the most primitive object ever explored by a spacecraft. The I/F of Arrokoth is analyzed and fit with a photometric function that is a linear combination of the Lommel-Seeliger (lunar) and Lamber...

On January 1st 2019, the New Horizons spacecraft flew by the classical Kuiper belt object (486958) Arrokoth (provisionally designated 2014 MU69), possibly the most primitive object ever explored by a spacecraft. The I/F of Arrokoth is analyzed and fit with a photometric function that is a linear combination of the Lommel-Seeliger (lunar) and Lamber...

The outer Solar System object (486958) Arrokoth (provisional designation 2014 MU$_{69}$) has been largely undisturbed since its formation. We study its surface composition using data collected by the New Horizons spacecraft. Methanol ice is present along with organic material, which may have formed through radiation of simple molecules. Water ice w...

Examining Arrokoth The New Horizons spacecraft flew past the Kuiper Belt object (486958) Arrokoth (also known as 2014 MU 69 ) in January 2019. Because of the great distance to the outer Solar System and limited bandwidth, it will take until late 2020 to downlink all the spacecraft's observations back to Earth. Three papers in this issue analyze rec...

Examining Arrokoth The New Horizons spacecraft flew past the Kuiper Belt object (486958) Arrokoth (also known as 2014 MU 69 ) in January 2019. Because of the great distance to the outer Solar System and limited bandwidth, it will take until late 2020 to downlink all the spacecraft's observations back to Earth. Three papers in this issue analyze rec...

We present results from numerical simulations of the DART impact using the CTH shock physics code with 2D homogenous asteroid models. A design of experiments approach was used to create a run matrix of 28 simulations varying 17 different material model inputs for the impactor and target. The resulting values of the momentum transfer efficiency fact...

The LOng Range Reconnaissance Imager (LORRI) is a panchromatic (360--910 nm), narrow-angle (field of view = 0.29 deg), high spatial resolution (pixel scale = 1.02 arcsec) visible light imager used on NASA's New Horizons (NH) mission for both science observations and optical navigation. Calibration observations began several months after the NH laun...

Plain Language Summary Space around Pluto is not entirely empty but filled with solar wind plasma and ions that originate from interstellar space and are pushed outward by the solar wind. All planetary bodies interact with their surrounding medium. In the case of a magnetized body like Earth, this interaction is strong and creates a magnetosphere....

The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe...

Suprathermal ions form from interstellar gas that is first ionized into pickup ions and then accelerated to tens and hundreds of keV in energy. The resulting suprathermal ion spectra with hundreds of keV have been previously observed throughout the heliosphere; however, measurements at lower energies, around the pickup ion cutoff energy where they...

The Asteroid Impact Deflection Assessment (AIDA) collaboration is a joint ESA-NASA planetary defense collaboration that will include the first full-scale test of an asteroid deflection by kinetic impactor [1]. The AIDA collaboration comprises two independent spacecraft, the NASA-sponsored Double Asteroid Redirection Test (DART) and the ESA-led Hera...

The Asteroid Impact & Deflection Assessment (AIDA) targets binary near-Earth asteroid (65803) Didymos. As part of this mission, the NASA-led Double Asteroid Redirection Test (DART) will make a kinetic impactor collide with the smaller secondary of Didymos to test kinetic impact asteroid deflection technology, while the ESA-led Hera mission will eva...

The New Horizons spacecraft extended the range in solar phase angle coverage for Pluto's moon Charon from 1.°8 - the maximum observable from Earth - to 170°. This extraordinary expansion in range has enabled photometric modeling and a robust determination of Charon's phase integral and Bond albedo at visible wavelengths. Photometric modeling shows...

Geologic mapping has been used for over 200 years as a technique to synthesize a complicated surface into a more simplified product, identifying similar types of surface features, and placing them into a relative stratigraphy. Geomorphologic mapping has applied those principles to other terrestrial bodies throughout the solar system and has formed...

This paper describes the evolution of the NASA Double Asteroid Redirection Test (DART) mission design and navigation. Specifically, the mission has been conceived as (1) a hydrazine bus on a ballistic trajectory, (2) a low-thrust bus launching from a geostationary transfer orbit and spiraling to escape, and (3) a low-thrust bus that launches with a...

Recent observations of interplanetary medium atomic hydrogen Lyman-α emission in the outer solar system, made with the Alice ultraviolet spectrograph on New Horizons, are presented. The observations include regularly spaced great circle scans of the sky and pointed observations near the downstream and upstream flow directions of interstellar H atom...

The New Horizons encounter with the cold classical Kuiper Belt object (KBO) 2014 MU69 (informally named 'Ultima Thule,' hereafter Ultima) on 1 January 2019 will be the first time a spacecraft has ever closely observed one of the free-orbiting small denizens of the Kuiper Belt. Related to but not thought to have formed in the same region of the Sola...

Recent observations of interplanetary medium (IPM) atomic hydrogen Lyman-{\alpha} (Ly{\alpha}) emission in the outer solar system, made with the Alice ultraviolet spectrograph on New Horizons (NH), are presented. The observations include regularly spaced great-circle scans of the sky and pointed observations near the downstream and upstream flow di...