[Paper Review] An investigation of the low-DeltaV near-Earth asteroids (341843) 2008 EV5 and (52381) 1993 HA. Two suitable targets for the ARM and MarcoPolo-M5 space missions

D. Perna, Marcel Popescu+4 more|arXiv (Cornell University)|Oct 4, 2016

Astro and Planetary Science28 references5 citations

TL;DR

This study investigates two low-DeltaV near-Earth asteroids, (341843) 2008 EV5 and (52381) 1993 HA, as prime targets for NASA's Asteroid Redirect Mission (ARM) and ESA's MarcoPolo-M5 sample return mission. Using visible and near-infrared spectroscopy and photometry, the authors confirm 2008 EV5 as a C-type asteroid with a homogeneous surface and determine 1993 HA as a likely D-type with a 4.107-hour rotation period and elongated shape, making it an optimal target for sample return missions.

ABSTRACT

The Asteroid Redirect Mission (ARM) under development by NASA is being planned to collect a multi-meter boulder from a near-Earth asteroid (NEA), and to bring it to the cis-lunar space in the mid-2020's for future study and exploitation by a crewed mission. The MarcoPolo-M5 project is being proposed in 2016 for the M5 mission opportunity by ESA, to bring back to Earth a sample from a very primitive D-type NEA. We aim to further characterize the physical properties of two optimal targets for sample return space missions, the low-DeltaV NEAs (341843) 2008 EV5 and (52381) 1993 HA. 2008 EV5 is the baseline target of ARM, but only one spectrum of this object exists in the literature. 1993 HA is a very favourable target for a space mission based on its dynamical properties: here we intend to assess if it is a suitable target for MarcoPolo-M5. We obtained visible spectroscopy of 2008 EV5 with the FORS2 instrument at ESO-VLT, at different rotational phases. We also obtained visible and near-infrared spectroscopy of 1993 HA, using the EFOSC2 and SOfI instruments at ESO-NTT. Visible photometry of 1993 HA was carried out within the IMPACTON project at the Observatorio Astronomico do Sertao de Itaparica (Brazil). Our new observations are in agreement with the C-type classification of 2008 EV5. We obtained five visible spectra which do not show any variability within the limits of noise, suggesting a homogeneous surface. We obtained the first ever spectroscopic dataset for 1993 HA, finding a featureless, red-sloped behaviour typical of D-types. We found that the synodic rotation period of 1993 HA is 4.107+-0.002 h. The derived lightcurve also suggests an elongated shape (axis ratio a/b>=1.71). At this stage 1993 HA does indeed seem to be the most favourable target for MarcoPolo-M5, though future observations are necessary to study it further.

Motivation & Objective

• To confirm the C-type classification of (341843) 2008 EV5, the baseline target for NASA's ARM mission, using new visible spectroscopy.
• To assess the suitability of (52381) 1993 HA as a target for ESA's MarcoPolo-M5 sample return mission based on its physical and dynamical properties.
• To determine the synodic rotation period and shape constraints of 1993 HA through photometric lightcurve analysis.
• To characterize the surface composition of both asteroids using visible and near-infrared spectroscopy to evaluate their scientific value for sample return.
• To provide critical pre-mission data for mission selection, especially given the limited observation window before ARM target finalization.

Proposed method

• Acquired five visible spectra of 2008 EV5 using the FORS2 instrument on the ESO Very Large Telescope (VLT) at Paranal, Chile, at different rotational phases.
• Obtained visible and near-infrared spectroscopy of 1993 HA using EFOSC2 and SOfI instruments on the ESO New Technology Telescope (NTT) at La Silla, Chile.
• Conducted visible photometry of 1993 HA within the IMPACTON project using the Observatório Astronômico do Sertão de Itaparica in Brazil.
• Analyzed the spectral data to classify the taxonomic type of both asteroids, focusing on absorption features and spectral slope.
• Fitted the lightcurve of 1993 HA to derive its synodic rotation period and estimate its triaxial ellipsoid shape using amplitude and phase information.
• Evaluated mission feasibility by comparing the Delta-V values and mission durations for both targets against mission requirements for ARM and MarcoPolo-M5.

Experimental results

Research questions

• RQ1 Is (341843) 2008 EV5 a homogeneous C-type asteroid, as required for the ARM mission, based on multi-phase spectroscopy?
• RQ2 What is the surface composition of (52381) 1993 HA, and does it qualify as a D-type asteroid suitable for the MarcoPolo-M5 sample return mission?
• RQ3 What is the synodic rotation period of 1993 HA, and does it fall within the optimal range for sample return mission operations?
• RQ4 What shape constraints can be derived from the lightcurve of 1993 HA, and does it indicate an elongated or spherical morphology?
• RQ5 How do the dynamical properties (Delta-V, mission duration) of 1993 HA compare to mission requirements for MarcoPolo-M5 and ARM?

Key findings

• The five visible spectra of 2008 EV5 show no detectable variability within noise limits, confirming a homogeneous surface consistent with a C-type classification.
• The visible and near-infrared spectroscopy of 1993 HA reveals a featureless, red-sloped spectrum typical of D-type asteroids, with a T-type or X-type classification possible at lower confidence.
• The synodic rotation period of 1993 HA is measured as 4.107 ± 0.002 hours, an optimal value for sample return mission operations.
• The lightcurve of 1993 HA implies an elongated shape with a minimum axis ratio a/b ≥ 1.71, indicating a triaxial ellipsoid with significant asphericity.
• The Delta-V for 1993 HA is 5.3 km/s, and the mission duration is estimated at 3.6 years, making it one of the most accessible and favorable targets for the MarcoPolo-M5 mission.
• Despite its low albedo and moderate brightness, 1993 HA is expected to reach V = 19.2 mag in April 2019, enabling further observations to refine its physical properties.