Measurement requirements for a near-Earth asteroid impact mitigation demonstration mission (1107.4229v1)

Abstract: A concept for an Impact Mitigation Preparation Mission, called Don Quijote, is to send two spacecraft to a Near-Earth Asteroid (NEA): an Orbiter and an Impactor. The Impactor collides with the asteroid while the Orbiter measures the resulting change in the asteroid's orbit, by means of a Radio Science Experiment (RSE) carried out before and after impact. Three parallel Phase A studies on Don Quijote were carried out for the European Space Agency: the research presented here reflects outcomes of the study by QinetiQ. We discuss the mission objectives with regards to the prioritisation of payload instruments, with emphasis on the interpretation of the impact. The Radio Science Experiment is described and it is examined how solar radiation pressure may increase the uncertainty in measuring the orbit of the target asteroid. It is determined that to measure the change in orbit accurately a thermal IR spectrometer is mandatory, to measure the Yarkovsky effect. The advantages of having a laser altimeter are discussed. The advantages of a dedicated wide-angle impact camera are discussed and the field-of-view is initially sized through a simple model of the impact.

• The paper demonstrates key measurement requirements for precisely determining momentum transfer and orbital changes after an asteroid impact.
• The study details a dual-spacecraft approach using a Radio Science Experiment and thermal infrared spectrometry to monitor the Yarkovsky effect.
• The methodology emphasizes calibrating solar radiation pressure and gravitational harmonics to optimize mission performance and reduce uncertainties.

Measurement Requirements for Near-Earth Asteroid Impact Mitigation

The paper by Wolters et al. provides an extensive review of the measurement requirements for the potential Don Quijote Impact Mitigation Preparation Mission to a Near-Earth Asteroid (NEA). This mission concept, which emerged from the European Space Agency's exploration of impact mitigation strategies, involves sending two spacecrafts: the Impactor, which collides with the asteroid, and the Orbiter, designed to measure the resultant change in the orbit via a Radio Science Experiment (RSE).

Mission Objectives and Payload Requirements

The mission's agenda is split into primary and secondary objectives. The primary objective focuses on altering the asteroid's semi-major axis by over 100 meters with an accuracy of measurement at a 1% threshold. This requires a precise determination of the momentum transfer from the impact, factoring in the asteroid's mass, size, bulk density, and rotation state. Additionally, a multi-spectral mapping of the asteroid forms the secondary objective of the project.

A crucial aspect of this paper is the emphasis on thermal infrared (IR) measurements to accurately assess the asteroid's orbital change as affected by the Yarkovsky effect, a non-gravitational force due to thermal emissions. The integration of a thermal IR spectrometer is mandated, aiding in quantifying this effect over time to distinguish its influence from direct impact measurements. The paper indicates a predicted draught in semi-major axis ranging significantly for target asteroids 2002 AT4 and (10302) 1989 ML.

Radio Science Experiment

The RSE, pivotal to mission success, involves detailed measures of the asteroid's gravitational field and mass distribution. The accuracy of these parameters is inherently tied to minimizing uncertainties, especially those posed by solar radiation pressure (SRP). This paper demonstrates the necessity of characterizing SRP with precision, leveraging a thorough knowledge of spacecraft surface properties and dynamic reflection coefficients.

The gravitational attraction modeling for both asteroids (2002 AT4 and 1989 ML) under different axial ratios and probable GM values verifies the challenge in harmonics measurement, stressing that measurements must commence as early as possible.

Implications for Impact Mitigation Strategy

The paper’s impact extends to future NEA mitigation strategies by pushing for an Impact Interpretation Objective, intermediate between primary and secondary mission objectives. This instance supports payload instruments that calibrate the impact mechanics and collect data on near-surface properties, such as bulk density, grain size, and ejecta dynamics. An Impact Camera, possibly with polarimetry capability, is highlighted as pivotal for recording the impact plume dynamics and interpreting ejecta characteristics in detail.

Recommendations and Future Applications

From a practical standpoint, carrying a mapping camera and a laser altimeter is argued as advantageous, providing synergistic benefits in geospatial mapping and orbital modeling while diminishing data acquisition complexities. The proposed operational timeline, including distinct phases from initial drift-bys to subsequent RSE campaigns, addresses instrumental efficiency over mission duration.

Reflecting on the broader implications, this research underscores the complexity of asteroid impact mitigation missions and the interdisciplinary cooperation required to deal with celestial mechanics, spacecraft design, and observational astrophysics. Moreover, the mission could lay groundwork for future NEA deflection missions by mitigating uncertainties in modeling ejecta behavior and Yarkovsky effects.

In conclusion, this paper provides a meticulous evaluation of the instrumentation and operations necessary for a successful asteroid impact mitigation mission. These insights are not only valuable for the theoretical modeling and operational planning of such missions but also for the advancement of planetary defense technologies. Future developments might witness enhanced mission design principles and more sophisticated payloads capable of executing complex observational and modeling tasks central to advanced asteroid deflection endeavors.