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mall satellites including cubesats, which are constructed from one to six conjoined 10-cm cubes, and nanosatel-lites, which are often in multi-cube for-mat and are defined as having total mass between 1 and 10 kg, offer increasingly sophisticated in-situ space experiment implementation and analytical measure-ment capabilities. Recent advances in miniature, micro, and integrated tech-nologies support the development of small payload systems that can be ac-commodated on these small satellites (Woellert et al. 2010); accordingly, min-iaturized instruments and microanalyti-cal systems are driving the capability of small-satellite science missions forward by harnessing recent advances in micro-fluidics, microelectromechanical systems (MEMS) including sensors and actuators, polymer microfabrication technologies, low-power microelectronics, high-effi-ciency solar cells and miniature motors, advanced materials, and integrated/fiber optics including micro/miniature light sources, cameras, and spectrometers. As a result, small, lightweight, low-power, inexpensive instrumentation adaptable to many science and technology applica-tions is being integrated into cubesat and nanosatellite payloads that can return sci-ence data from outer space at a fraction of the cost of traditional large-spacecraft missions.Astrobiology comprises the study of the
origins, evolution, distribution, and future of life in the universe and is amenable to a variety of space science experimentation implemented with small satellites. In or-der to demonstrate such implementation and supporting technologies, NASA Ames Research Center launched the 3U (one “U” being a 10-cm cube) cubesat called O/ OREOS (Organism/Organic Exposure to Orbital Stresses) in 2010 to a 72°-inclina-tion, 650-km Earth orbit as a secondary payload aboard a Minotaur IV rocket from Kodiak, Alaska, USA. O/OREOS consists of three conjoined cubesat modules (each being 1U): the control bus, a payload to test the multi-month viability of mi-crobes, and a payload to study in-situ the time-dependent degradation of organic molecules over the course of at least six months. O/OREOS is still in orbit but will not return to Earth; it will disintegrate upon atmospheric re-entry in approxi-mately 2032.
The O/OREOS spacecraft is equipped with a passive attitude control system that utilizes multiple permanent magnets to orient its main “patch” antenna toward ground stations when above the northern hemisphere, along with magnetic hyster-esis rods that damp rotational and nuta-tional energy. The spacecraft utilizes two radios, one a UHF transmit-only “beacon” (437 MHz), the other a two-way S-band ra-dio. Amateur operators from 22 countries contributed to the mission by collecting
over 100 000 data packets from O/OREOS and submitting them to the website oper-ated by the mission operations team (Kitts et al. 2011). Science data downlink and command and control uplink utilize the S-band radio, which transmits and receives using conventional 2.4-GHz WiFi technol-ogy via the main 5 x 5 cm patch antenna. Science data were retrieved frequently (on a daily basis) early in the mission by the Mission Operations Center at the Ro-botic Systems Laboratory of Santa Clara University, using a pair of 3-m dishes on campus to communicate directly with the satellite. O/OREOS is the first nanosatel-lite to carry a biological payload to such a high altitude. To meet NASA and UN orbital debris management requirements (decay < 25 years after end of mission), O/OREOS includes a self-deploying “Na-noKite” that increases its surface area by over 50% but adds only a few percent to its mass, resulting in the estimated year of de-orbit of 2032. Full O/OREOS mission success, as defined by NASA technology readiness level (TRL) 8, including launch, successful operation of both payloads, and download of collected mission data, was achieved in May 2011 (Kitts et al. 2011, Ehrenfreund et al. 2013).
SCIENCE ABOARD THE O/OREOS NANOSATELLITE
The Space Environment Survivability of Living Organisms (SESLO) experiment
col-Cubesats: powerful science platforms for space exploration
The improvements in the miniaturization of spacecraft and spacecraft subsystems
have resulted in a wide variety of small satellites and nanosatellites. This has opened
the door to inexpensive, lightweight, small and flexible satellites and missions with
various scientific applications. One such application could be the use of CubeSats for
astrobiological research.
TEXT Dr. P. Ehrenfreund, Leiden Institute of Chemistry; A. Elsaesser, Leiden Institute of Chemistry; A.J. Ricco, NASA Ames Research Center
ASTROBIOLOGY RESEARCH WITH CUBESATS
ESA
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lected data on the survival and metabolicactivity of microbes at 3 times during the 6-month mission (Nicholson et al. 2011). The payload consists of three “bioblock” modules, each with twelve 75-µL sample wells connected by microfl uidic channels and valves that allow the introduction of germination-and-growth media. Using 3-color LED illumination (470, 525, and 615nm), the growth and metabolism de-tails of Bacillus subtilis microbial spores, exposed to the microgravity, ionizing radiation, and heavy-ion bombardment of the high-inclination orbit, were deter-mined. The SESLO spacefl ight experiment has met or exceeded all its originally spec-ifi ed mission requirements. Spore germi-nation and growth were achieved after 14 and 97 days in space with little diff erence in behavior between these two times. The fi rst results also indicated that the cells in microgravity generally grow and metabo-lize more slowly than those subjected to Earth gravity, a diff erence tentatively as-cribed to the gravitation dependence of certain aspects of the solution transport of nutrients and/or waste products. The Space Environment Viability of Organ-ics (SEVO) experiment achieved real-time analysis of the photostability of organic molecules. The samples were depos-ited as thin fi lms by vacuum sublimation onto MgF2 windows. The SEVO payload consists of a miniaturized UV-visible-NIR spectrometer and a 24-sample carousel that houses hermetically sealed sample cells (Bramall et al. 2012). Integrated op-tics enables the use of the Sun as the light source for both sample radiation expo-sure and sample spectroscopic meaexpo-sure- measure-ment. The SEVO payload was designed to acquire UV-visible spectra automatically when onboard sensing determined that its sample wheel and collection optics
were pointed within a few degrees of the direction of the Sun. The molecular spe-cies absorption lines in both the solar and SEVO spectra indicated excellent wave-length calibration of the spectrometer. The SEVO payload returned spectral data sets from 18 organic thin fi lms over ten months of space exposure that show sig-nifi cant changes in the absorbance of the fi lms due to photochemical degradation (Mattioda et al. 2012; Cook et al. 2013a). Thin-fi lm reaction rate data and other spectral information measured in situ in combination with ground-based experi-ments and modeling have been used to characterize reaction mechanisms perti-nent to the SEVO microenvironments and related space environments (Mattioda et al. 2012; Cook et al. 2013a,b).
CUBESAT TECHNOLOGY APPLICATIONS FOR THE ISS
Some of the technologies that have been recently demonstrated on small satellites are ideal payload candidates for accom-modation on the International Space Station (ISS). A recent example of a rap-id-turnaround payload is the OREOcube experiment, which is based on O/ORE-OS-SEVO technology described above. OREOcube will be installed as an external exposure facility on the ISS under the Eu-ropean Space Administration’s EuEu-ropean Programme for Life and Physical Sciences in Space (ELIPS) to study the evolution of organic and prebiotic materials in space. OREOcube is prepared for fl ight in coop-eration between Leiden University and NASA Ames Research Center and can re-cord daily changes in ultraviolet and vis-ible light absorption spectra of organic compounds, revealing the consequences of their exposure to solar UV, visible light and space ionizing radiation. The advan-tages over a free-fl yer experiment are
that data can be downloaded from the ISS more eff ectively and frequently with on-board data averaging and storage ca-pability using a standard power-and-com-mand interface. Additionally, the samples can be retrieved and be further analyzed in terrestrial laboratories.
CONCLUSION
The number of research areas for cube-sats is ever increasing and includes apart from astrobiology many experiments that investigate atmospheric science, astron-omy, exoplanets, planetary science, biol-ogy, pharmaceutical applications, Earth observations, ecology, materials science, and space weather. In the fi eld of astro-biology in particular, signifi cant progress has been achieved with the success of the O/OREOS mission. Cubesat payload can serve as precursors for experiments on the ISS, future free-fl ying satellites, and planetary surface exposure facilities. As discussed by Rose et al. (2012), merg-ing the cubesat university culture with proven space-qualifi ed engineering tech-niques without losing the cost-eff ective innovative advantages, while challenging, will lead to more advanced science cube-sats. The “Nanoracks” facility on the ISS already accommodates cubesat science payload instrumentation with power and data-transfer interfaces. Future applica-tions for cubesat technology are under consideration for hitchhiking on planetary exploration missions in the framework of cubesat dispensers on Mars orbiters, cube accommodation slots on various landers, and possible outer-solar-system research activities. The science capabilities of cube-sats are rapidly expanding along with the demands of various research fi elds with appropriate applications in low Earth or-bit and beyond.
CA N A D IA N S PA CE A G EN C Y ESA NASA
Figure 1. Assembly of O/OREOS Satellite
