AMBASSADOR: Asteroid sample return mission to 7 Iris

Abstract

The primary goal of the AMBASSADOR (A Main Belt Asteroid Seismic study and Sample Acquisition to Determine meteorite ORigins) mission to S-class asteroid 7 Iris to determine the relationship between asteroids of this class and meteorites. This goal will be accomplished through collection of surface samples to be returned to Earth and acquisition of high-resolution visible and near-infrared (NIR) spectral images of the asteroid's surface. AMBASSADOR will also constrain the internal structure of Iris by deploying a seismic network on the asteroid and conducting an active seismic experiment. The importance of such a mission is emphasized by its inclusion as an element of the “Building Blocks and Our Chemical Origins” Campaign of the NASA Roadmap, although currently no missions comparable to AMBASSADOR exist. AMBASSADOR is a two-component spacecraft comprising an orbiter and a lander that will travel together to Iris. The orbiter will carry a visible and NIR spectral camera which will perform global mapping of the asteroid at resolutions of ~28 m/pixel and -112 m/pixel, respectively. High-resolution imaging of several sites of interest, including potential landing sites, will be conducted at resolutions of ~1.4 m/pixel in the visible and ~5.4 m/pixel in the NIR. The orbiter will also deploy four penetrators each of which will include a seismometer and a transmitter and will be accompanied by an explosive charge. After selection of a landing site, the lander will separate and descend to the asteroid where it will perform imaging experiments and collect samples. Material will be collected by two different mechanisms: a chipping device able to collect regolith and coring devices able to collect samples from a solid surface. The lander will carry a camera similar to that on the orbiter to image the surface at sub-millimeter resolution before and after sample collection. Following surface operations, the lander will launch from the asteroid and redock with the orbiter for return to Earth. The major new technologies necessary for AMBASSADOR are in the subsystems propulsion, power, and attitude determination and control (ADC). Solar electric propulsion (SEP) makes the AMBASSADOR mission possible; when compared to strictly chemical propulsion, SEP reduces the mission duration from 17 years to five years and also increases the fraction of the launch mass that can be returned to Earth. The power requirements of SEP engines are quite high; thus, power will be provided by next generation copper-indium-selenium, thin film, amorphous mylar solar arrays. To enable autonomous landing, the ADC subsystem on the lander will include a stereo imager and a laser range-finder. For autonomous rendezvous and re-docking, both the lander and the orbiter will be equipped with formation flying sensors and the lander will be equipped with a docking camera while the orbiter will carry a target.