SKY_September2014.pdf

(Axel Boer) #1
16 September 2014 sky & telescope

News Notes

MISSIONS I Kepler Spacecraft Starts New Mission


NASA’s crippled planet-hunting space-
craft is back in business and commis-
sioned for at least two years of productive
new science.
When the second of four reaction wheels
seized up in May 2013 (S&T: Aug. 2013, p.
10), the Kepler spacecraft’s observing days
seemed over. To observe with its hallmark
accuracy, the spacecraft must control its
position in three dimensions, which nor-
mally requires three gyroscopes.
However, scientists and engineers
quickly came up with a Plan B: combine
solar radiation pressure and the two func-
tioning reaction wheels to stabilize the

spacecraft’s pointing.
In May, NASA approved the new
mission, dubbed K2. K2 is a community-
driven mission, with targets taken solely
from astronomers’ proposals. It will take
advantage of the spacecraft’s changing
fi eld of view, which not only must stay
confi ned to the ecliptic plane (due to the
reliance on sunlight’s feeble pressure) but
also must migrate around the sky as it
orbits the Sun (see the diagram above).
Kepler’s new attitude expands the
range of its scientifi c research. Over the
next two years, the spacecraft will watch
nine fi elds of view, including populous
star fi elds in the Milky Way and active
galactic nuclei. Each campaign will last
approximately 80 days, with four to fi ve
campaigns fi tting into each 372-day orbit
around the Sun.
Campaign 1 lasted from May 30th
until August 1st and focused on the North
Galactic Cap. Subsequent campaigns will
examine notable near-ecliptic star clusters,
such as the Pleiades (M45) and the Hyades
(Campaign 4) and the Beehive Cluster
(M44) and M67 in Cancer (Campaign 5).
Mission planners are still requesting input
for targets for the fi nal four campaigns, so
the exact coordinates for future campaigns
are not yet set in stone.
“If you don’t propose it, we don’t do it,”
said Martin Still (NASA Ames Research

Galactic Plane

Declination

Right Ascension

0 h 22 h 20 h 18 h 16 h 14 h 12 h 10 h 8 h 6 h 4 h 2 h 0 h

–40°

–30°

–20°

–10°

10 °

20 °

30 °

40 °

0 ° PISCES

TAURUS

ARIES

GEMINI

CANCER

LEO

VIRGO

LIBRA
SAGITTARIUS

CAPRICORNUS

AQUARIUS

SCORPIUS

OPHIUCHUS
PISCES

Field 8

Field 4

Field 0
(trial run)

Field 5

Field 1

Field 6
Field 7

Field 3

Field 9

Uranus

M
M

M

Neptune

Hyades

Uranus

Neptune Field 2

2016 Fields

2015 Fields

2014 Fields

Above: The Kepler spacecraft will observe nine
campaign fi elds over the next two years, follow-
ing the ecliptic plane due to its mechanical limp.

Center) on June 3rd at the American
Astronomical Society meeting in Boston.
“There are no guaranteed targets.”
NASA has allocated $4 million for K
guest observers over the next two years.
All data will be freely accessible through
the Mikulski Archive for Space Telescopes
and the NASA Exoplanet Archive.
Not everything is smooth sailing for
the new mission. The fact that the space-
craft observes near the ecliptic means that
bright solar system objects will occasion-
ally move across the fi eld — Mars passes
right through Campaigns 2 and 3, for
example. The glare and refl ections can
degrade the data. Additionally, the noise
level in K2’s photometry is 1½ to 2 times
stronger than in the original mission.
The aim point also drifts slightly, so
mission planners must fi re the space-
craft’s thrusters every 6 hours to com-
pensate. This “roll and reset” method will
aff ect the photometry, said Tom Barclay
(NASA Ames Research Center), but this
can be accounted for in the data analysis.
■ MARIA TEMMING

Read more about NASA’s new K
mission at skypub.com/k2works.

NASA K2 MISSION (2)

K2 Pointing for
Campaigns

Co

nti
nu
e^.^

.^.^


Campaign (^) #
(^2)
(^)
Ca
m
pa
gi
n
1 #
Spacecraft rotated to
prevent sunlight from
entering scope
END, DAY 83
Solar panel
illuminated
START, DAY 1
Field of View



Field of
View #
Sun
NN_layout.indd 16 6/23/14 12:20 PM

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