IEEE - Aerospace and Electronic Systems - March 2020 - 8

BioSentinel: A 6U Nanosatellite for Deep-Space Biological Science
Table 1.

Ionizing Radiation Dose Rates for Various Regions of Outer Space

Orbit

LEO
ISS in LEO
High-inclination
LEOd
Sun-synchronous
LEO, incl. polar
Lunar orbitf
Interplanetary
spaceg

Altitude (from
Earth's surface, km)

300-2000
330-435

Inclination

0 -55

e-, pþ

90-127 min

91-93 min

51.6

Orbital period
about Earth

Particlee
radiation
sources

e ,p
þ

Shielding-dependent
monthly radiation dose
rangeb (Gy)
1 mmc

5 mmc

0.0061-660

0.0041-36

5-30

0.34-0.020

400-2000

65 -115

92-127 min

e , p , GCRs,
SEPs

40-1500

0.69-140

400-1000 (typical)

$98 and
others

92-105 min

e-, pþ, GCRs,
SEPs

40-180

0.86-10

perigee: 363 104
apogee: 405 700

27 d

GCRs, SEPs,
n0

7.7-96

0.38-15

N/A

GCRs, SEPs

11-140

0.55-21

> $ 100 000

a
0 -90 inclinations are prograde orbits; 90 -180 are retrograde orbits. bAssuming an exposure over a solid angle of 4p steradians for 30
days, midway between solar minimum and maximum; dose can vary widely due to solar activity. Data sources and models are described in
[2]. cShielding expressed as equivalent thickness of aluminum. dIncludes orbits near latitudes of Arctic/Antarctic circles, including polar
and near-polar orbits. ePredominant sources; e- ¼ electrons, pþ ¼ protons, n0 ¼ neutrons; GCR ¼ galactic cosmic ray; SEP ¼ solar energetic particle. fRadiation estimates are for a 50-km lunar orbit about the Moon with a 113-min orbital period. gGenerally representative of
transit to a variety of locations around the solar system, including Mars, its moons, the moons of Jupiter, and various near-Earth objects.

wild-type strains, the effects of radiation upon the DNA
DSB repair process can be monitored.

INTRODUCTION TO THE SCIENCE MEASUREMENTS OF
BIOSENTINEL
NASA's BioSentinel mission is the first step in an emergent
effort to understand the impacts of the deep-space environment in situ by sending terrestrial organisms to live beyond
the radiation shield of Earth's magnetic field and monitoring their responses. The BioSentinel Nanosatellite, a 6U

Figure 1.
Solid model of BioSentinel 6U nanosatellite in interplanetary space.

deep-space cubesat housing microorganisms grown and
characterized as a function of the type and amount of radiation to which they are exposed over a duration of three to
nine months in space, is due to launch in 2020. It is the sole
biological mission among the secondary payloads on
NASA's Artemis-1, planned to be carried into space by
NASA's Space Launch System (SLS). Upon ejection from
the launch vehicle upper stage following Orion capsule
separation, BioSentinel will be deployed on a trajectory
that results in a lunar flyby leading to a (permanent) heliocentric orbit well beyond Earth's magnetic field and radiation belts. A companion mission scheduled to operate in
LEO aboard the International Space Station (ISS), safely
within the geomagnetic field, along with an identical
ground-control payload, will enable comparison of the
radiation environments of deep space, LEO, and Earth; the
three locales also provide controls for effects related to two
gravitational environments, i.e., micro-g (on ISS and the
BioSentinel Nanosatellite) and terrestrial gravity.
The comparative rates of growth and metabolism of
specimens of radiation-sensitized and wild-type yeast will
be assessed in BioSentinel's first payload, a microfluidicsenabled system with independent temperature-controlled
culture microwells. Multiple replicate cultures of both
strains are loaded and dried in the microwells in microfluidic
minicards prior to flight, then activated over a series of timepoints spanning the mission duration. Until the time of their
growth, each grouping of microwells is maintained in a state
of low-humidity, low-temperature stasis-much as baker's
yeast are preserved in the refrigerator-to promote

IEEE A&E SYSTEMS MAGAZINE

MARCH 2020

IEEE - Aerospace and Electronic Systems - March 2020

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