I I I NEAR BARTH ASTEROID RETURNED SAMPLE MISSION I (NEARS) A. F. Cheng and S.R. Vernon* The Johns Hopkins University I Applied Physics Laboratory Laurel, Maryland 20723-6099 I I I I I I I I I I I I *Member, AIM I 1 I I I Abstract I NEARS is a small mission The NEARS mission will use to be proposed for the NASA a Delta II 7925 to launch in Discovery Program. It will January 2000 to the primitive I use a modified version of the (probably C-type) asteroid 4660 Near Earth Asteroid Rendezvous Nereus. Earth return occurs 4 spacecraft being developed by years later. The return the Johns Hopkins Applied capsule will use Pioneer Venus I Physics Laboratory. The NEARS heritage and will be supplied mission will return a set of by Martin Marietta Astrospace. samples from a near-Earth The pre-Phase A study of the I asteroid to Earth for analysis NEARS mission was supported by in terrestrial laboratories. the NASA Solar System NEARS will be the first sample Exploration Division. return from outside the We are currently I Earth-Moon system and will be a developing a sample acquisi tion pathfinder for future sample device that will be sui table returns from other small bodies for NEARS. This instrument I in the Solar System. NEARS development is supported by the will also be the first space NASA Planetary Instrument resource assessment beyond the Definition and Development I Moon and the first assessment Program. The sampler is a of the surface physical pyrotechnic device that will be properties of a small body. capable of obtaining a core With samples from a near-Earth sample from rock or regolith I asteroid, our laboratory surfaces. It does not require knowledge of materials from the spacecraft to tether itself specifically identified sources to the surface of the asteroid I will be extended beyond the and does not require a manned Moon to Earth's next nearest presence. The NEARS spacecraft neighbors. NEARS will will carry six of these establish the first detailed samplers, integrated with the I history for another body beyond return capsule, in a cluster the Earth and Moon and will be called the "six-shooter". We the decisive experiment for will present the NEARS mission I linking the fields of asteroid and spacecraft, the design and and meteorite science. test program for the sampler, and a systems integration and I packaging concept for the six-shooter. I I I 2 I I I I Introduction preparation for the release of the first Discovery Mission AO. NEARS is a low cost planetary NEARS is a follow-on to the mission to be proposed to the NEAR mission (wi th which it I NASA Discovery Program. should not be confused; the S The Discovery Program will in NEARS stands for Sample) consist of small planetary that will return a set of bulk I missions costing no more than samples from a near-Earth $150 million to launch plus 30 asteroid to Earth for analysis days, in 1'Y92 dollars. The in terrestrial laboratories. I first two missions in the NEARS is the logical next step, Discovery Program are the Mars after NEAR, in the scientific Pathfinder and the Near Earth explora tion of primi tive bodies As teroid Rendezvous (NEAR) • in the inner solar system. I Both of these missions were started in PY94 and will launch NEARS Consortium in 1996. The third and I subsequent missions in the The NEARS mission will be Discovery Program will be performed by a consortium selected competitively via the involving uni versi ty, industry, I Announcemen t of Opportuni ty and government partners. The (AO) process. Principal Investigator will be Eugene Shoemaker, of the Lowell The Discovery Program is Observatory, and formerly of I modeled after the Explorer the u.S. Geological Survey. Program for astrophysics and The Johns Hopkins Universi ty space physics. It is intended Applied Physics Laboratory I to enable rapid response to (APL) will provide the emerging scientific spacecraft, which will be opportunities; to increase the designed, fabricated, and I breadth of activities in solar integrated at APL. APL will system exploration, to enhance also provide the sample timeliness of new information collection system for NEARS, return; to provide increased perform spacecraft integration I access to space; to expand and test, and carry out industrial, academic, and mission operations. The Earth public involvement in solar return capsule will be designed I system exploration missions; and fabricated by Martin and to facilitate cooperative Marietta Astrospace at Valley ventures with other space Porge, PA. Martin Marietta I agencies. Missions in the Astrospace provided the reentry Discovery Program will capsules for the Pioneer Venus emphasize focused science. mission as well as the Jupiter They will have rapid Probe Galileo • The NASA Deep I development cycles, < 36 Space Network will be used for months, and will use launch telecommunications, and the vehicles no larger than a Delta lunar sample facility at the I 2. NASA Johnson Space Center will be responsible for curation and The NEARS mission was one of 14 distribution of samples. I mission concepts funded by NASA for pre-phase A studies in I 3 I I Science Rationale be extremely difficult to I establish clear relationships NEARS will be the first sample between specific meteorite return from outside the types and asteroid types on the I Earth-Moon system. It will basis of remote sensing of also be the first sample return asteroids. Only analysis of mission since the time of the asteroid samples in terrestrial Apollo missions. NEARS will be laboratories can definitively I a pathfinder for future robotic , . establish such a linkage, if in sample return missions and will fact any linkage exists. It is provide the first space quite possible that a returned I resource assessment from beyond asteroid sample will contain the Moon. With samples from a previously unknown material near Earth asteroid (NEA), our that is not currently I laboratory knowledge of represented in the meteorite extraterrestrial materials from collection. Any friable or specifically identified sources semi -volatile material on the will be extended beyond the surface of asteroids would most I Moon to Earth's next nearest likely not survive collisional neighbors. ejection from the asteroid and then hypersonic reentry through I The NEARS mission will return Earth's atmosphere, except in samples from multiple sites on the form of interplanetary dust an NEA and will lead to particles. I profound advances in our understanding of the early Mission Overview solar system and the processes and conditions leading to the NEARS will return to Earth I formation of the terrestrial samples of 10 to 100 grams each planets. NEARS will establish from four to six sites on a the first detailed history for near-Earth asteroid. It will I another body in the solar also perform a global sys tem beyond the Moon and wi 11 characterization of the be the decisive experiment for asteroid, including mass volume I linking the fields of asteroid and dens i ty determinations, and astronomy and meteorite it will study the geologic science. Meteorites are context of the sample sites. believed to be fragments of The obj ectives for NEARS are I asteroids, but it has proved to summarized in Table 1: I Table 1. Science Objectives Provide the f'1I'St direct and detailed petrological, chemical, age, and isotopic I characterization of a near Earth asteroid. Relate the asteroidal material to terrestrial, lunar, and meteoric materials Sample the asteroid regolith and characterize any exotic fragments I Identify heterogeneity in the asteroid's isotopic properties, age, and elemental chemistry I 4 I I I I The prime target for the NEARS The prime launch opportuni ty mission will be the asteroid for NEARS occurs in January, I 4660 Nereus, which has been 2000 to the asteroid 4660 reported to be a primitive ... Nereus • The launch vehicle C-type asteroid. The type will be a Delta 11-7925. The I identification for Nereus is backup mission opportun i ty is a regarded as tentative, but it January 2002 launch to 4660 is established that Nereus is Nereus, which can be I not an S - type asteroid. The accomplished with an identical NEAR mission target, 433 Eros, flight system design. The is an S - type, as are the two trajectory for the January, target asteroids for the 2000 pr~e mission opportunity I Galileo flybys, 951 Gaspra and is plotted in Figure 1. Both 243 Ida. Our current knowledge of these are ballistic of Nereus is summarized in traj ectories to be performed I Table 2. using conventional bipropellant propulsion systems. We are Table 2. NEARS Target also studying electric I Nereus 4660 propulsion options that would use arcjet propulsion systems. I Figure 1. 2000 Launch (4660) Nereus I Type: C? (definitely not Type S) I.--=b DtIpIUt ~ Perihelion: 0.953 AU 1I1G111O 12fZ1J01 Cs-a.11cm'1a1 AV.550mIa ReIum Arrive.....,. I Aphelion: 2.03 AU 111'1104 10120/01 Inclination: 11.43° . 2AU I H Magnitude: 18.3 \ \ Size: 1-kmclass j I ! Rotation: Unknown " ,,' / "~" SImp" Relum I TI'IIjectory I I I 5 I Figure 2 sketches an overview sensor to signal contact with I of the NEARS mission. After the surface. The complete arrival at Uereus in October, sample collection system (the 2001, the spacecraft will Rsix-shooterR) will comprise execute a slow flyby of the four to six samplers and is I asteroid and then enter mounted, as a single unit, rendezvous orbit. A global wi thin the Earth return characterization of the capsule.