Sky and Telescope - February 2017 - 10

NEWS NOTES

* To get astronomy news as it breaks, visit skypub.com/newsblog.

MISSIONS
1

ExoMars Lander Fails,
Orbiter Succeeds

1

3

3

S NASA's Mars Reconnaissance Orbiter
took this image (background) of Schiaparelli's
disastrous landing site on October 25th. Closeups highlight three impact locations, all within
1.5 km (0.9 mile) of one another: (1) the lander
itself, (2) potential fragments of the heat shield,
and (3) the parachute and back shell.

MISSIONS

Juno Enters Safe Mode
ON OCTOBER 18TH , right before its

second Jupiter flyby, NASA's Juno spacecraft unexpectedly stopped operations.
After much angst on the part of scientists and the public, engineers restarted
the craft successfully a week later and
said it was apparently healthy.
Juno switched to "safe mode" after a
software performance monitor rebooted
the onboard computer, which it's pro10

THE EXOMARS MISSION, a joint effort
of the European and Russian space
agencies (S&T: Oct. 2016, p. 22) has
met with only partial success. Although
the Trace Gas Orbiter reached the Red
Planet as intended, the descent of the
tagalong Schiaparelli lander turned into
a fatal plunge on October 19th, when a
glitch compromised the landing.
Designed as a technology demonstration for a planned 2020 rover, the
lander was programmed to transmit
data through all stages of descent. Based
on those data, atmospheric braking and
parachute deployment were flawless.
Then, about 90 seconds prior to landing, things went awry.
First, the module jettisoned its heat
shield and parachute early. Then miscommunication between the onboard
navigational system and radar erroneously told Schiaparelli it was near the
surface. So the braking rockets shut off
after burning for only 3 seconds rather
than the planned 60 seconds. At about 2
to 4 kilometers (1 to 2½ miles) above the
surface, Schiaparelli went into freefall.

grammed to do when "conditions are
not as expected," according to a press
release. It's still unclear what triggered
the electronic hibernation, but one possibility is two main-engine check valves.
Prior to the anomaly, engineers had
decided to keep the Jupiter probe in its
wide-ranging orbit for at least one more
pass until they could address an issue
with the valves controlling the spacecraft's fuel pressurization system. During a command sequence the team ini-

F E B R U A R Y 2 0 1 7 * SK Y & TELESCOPE

The lander slammed into Meridiani Planum at an estimated 300 km
per hour (186 mph) and most likely
exploded on impact. Orbiter images
revealed an ugly new crater on Mars
(#1 in the image at left), as well as two
other debris impacts (#2 and #3).
European Space Agency (ESA)
officials were careful to stress that
Schiaparelli was only intended as a
landing test. A software glitch should
be a relatively easy fi x, as opposed
to the prospect of re-engineering a
fundamental flaw in the hardware. But
ESA and its partner, Roscosmos, will
obviously want the upcoming ExoMars
rover to reach the Martian surface
intact. For now, the impact of Schiaparelli's performance on the future of the
ExoMars program is unclear.
Meanwhile, the Trace Gas Orbiter
(TGO) is safely looping around the Red
Planet and "working perfectly," said ESA
spacecraft operations manager Andrea
Accomazzo. The spacecraft fired its
braking rocket for 139 minutes, slowing
down by more than 1.5 km/s in order to
be captured by the planet's gravity.
TGO's current orbit is a highly
elongated loop that ranges in altitude
from 300 to 96,000 km (190 to 60,000
miles). Beginning in March, the orbiter
will begin a year-long process of repeatedly dipping into the uppermost Martian atmosphere, creating a controlled
drag that will gradually bleed away
orbital energy and shrink the ellipse. By
March 2018, the near-polar orbit should
be circular, with an altitude of 400 km.
■ DAVID DICKINSON

tiated, these valves should have opened
in a few seconds - but instead took
several minutes, explains Juno project
manager Rick Nybakken (Jet Propulsion
Laboratory). "We need to better understand this issue before moving forward
with a burn of the main engine."
Juno did execute an orbital adjustment on October 25th using its smaller
thrusters, in preparation for another
Jupiter pass on December 11th.
■ DAVID DICKINSON

N ASA / JPL- CA LTECH / UNIV ERSIT Y OF A RIZON A

2

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Sky and Telescope - February 2017

Table of Contents for the Digital Edition of Sky and Telescope - February 2017

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Sky and Telescope - February 2017 - Cover1
Sky and Telescope - February 2017 - Cover2
Sky and Telescope - February 2017 - 1
Sky and Telescope - February 2017 - Contents
Sky and Telescope - February 2017 - 3
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