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
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