Sky and Telescope - July 2018 - 9

SPACECRAFT

IN BRIEF

James Webb
Telescope Delayed
Until 2020

Update on the Aurora
Named STEVE
For years amateur astronomers have seen
and photographed a thin, faintly pink- or

NASA OFFICIALS HAVE

announced that the launch
of the James Webb Space
Telescope will be delayed
until approximately May 2020, slipping
more than a year from its previous goal
between March and June 2019.
To date, the agency has spent $7.3
billion on Webb's development. If the
mission's development costs go over the
$8 billion maximum that Congress set
in 2011, Congress will need to reauthorize the project. An independent review
will nail down the changes in cost and
schedule, and NASA will report its
assessment to Congress in late June.
The pieces of Webb are all complete;
what's costing time and money is the
often unpredictable "integration and
testing" phase. NASA ofﬁcials admit
that the initial schedule for this phase
was optimistic.
Some of the technical challenges
faced were instructive. For example,
the complex sunshield was torn during
testing, so engineers made changes to
its storage and deployment. Preventing
damage is crucial, as the shield protects
the telescope's sensitivity at near-infrared wavelengths.
There were also avoidable errors: A
transducer was incorrectly powered and
had to be replaced, resulting in a threemonth delay, and an incorrect solvent
was run through the propulsion system,

purple-colored ribbon that runs east-towest southward of the northern lights. (To
read about the discovery, visit https://
p This 2017 image shows all five tennis-courtsize, membranous layers of Webb's sunshield,
displayed in Northrop Grumman's clean room in
Redondo Beach, California. These will have to
fold into the Ariane 5 rocket fairing.

is.gd/aurorasteve.) Eventually dubbed

damaging valves and seals and necessitating their replacement. To avoid
future mistakes, NASA ofﬁcials outlined
plans to monitor contractor Northrop
Grumman more closely.
Webb is a top priority within the
astronomical community and represents NASA's largest international space
science project. Once it launches, the
6.5-meter near-infrared telescope will
orbit the Sun at the Lagrangian point
L 2, 1.5 million km farther out than
Earth. The telescope will peer farther
back in cosmic time than Hubble to see
the universe's ﬁrst stars and galaxies. Astronomers will also use Webb to
characterize nearby exoplanets.
The delay will have a broad impact
on the astronomical community, notes
associate administrator Thomas Zurbuchen, both in terms of perception and
actual cost. Nevertheless, he insists, he
doesn't want the agency to shy away
from large, complex projects: "I want us
to have ambition."

directly through a Steve ribbon in 2016,

■ MONICA YOUNG

the reentry, but NASA and the European

"Steve," neither amateurs nor researchers knew what the phenomenon was.
Analyzing data from the European Space
Agency's Swarm A satellite, which flew
Elizabeth MacDonald (NASA Goddard)
and colleagues suggest in the March 14th
Science Advances that the amateurs had
spotted the subauroral ion drift (SAID), a
rapid flow of charged particles through
Earth's atmosphere that's associated with
brightening aurora. However, scientists
had never known of visible emission from
SAIDs, and the radiation mechanism
remains unclear. In the meantime, the
visual phenomenon gets to keep its name:
STEVE, short for Strong Thermal Emission
Velocity Enhancement.
■ MONICA YOUNG

Tiangong 1's Remote
Reentry
China's first space station, Tiangong 1
(Chinese for "celestial palace"), reentered
Earth's atmosphere over the South Pacific
on April 2nd after almost seven years in
space. No humans reported witnessing
Space Agency mounted a campaign to

NORTHROP GRUMMAN CORPOR ATION

remotely monitor the space station in an

understanding of its shape, which Belton's team concludes could be anything
from a cigar to a fat pancake. For the
moment, either shape is equally likely.
'Oumuamua's overall spectrum and
apparent lack of outgassing imply that
it's rocky, which could mean that it
was ejected from the inner region of its
host solar system. Yet Sean Raymond
(University of Bordeaux, France) and
others argue in the May 21st Monthly
Notices of the Royal Astronomical Society

that too few asteroidal fragments would
be ejected to make it statistically likely
for one to reach us, unless it was ejected
from a two-star system.
'Oumuamua may keep its secrets,
but chances are we'll ﬁnd another interloper soon: Calculations by Aaron Do
(University of Hawai'i) and colleagues
suggest that there are likely several of
these objects in the inner solar system
at any given time.

effort to better model future reentries.

■ J. KELLY BEATTY

■ DAVID DICKINSON

The reentry location was largely unknown
beforehand, complicated by the vehicle's
uncertain mass: While the media often
cited it as 8.5 metric tons, that number assumed a ton of fuel still onboard. Tracking
the reentry impressed upon scientists the
sensitivity of predictions to solar activity,
the state of Earth's thermosphere, and
atmospheric drag.

s k y a n d t e l e s c o p e . c o m * J U LY 2 0 1 8

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Sky and Telescope - July 2018

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