Sky & Telescope - December 2018 - 35

slight ground motions. In contrast,
slow and deliberate - from landing
SEIS will be directly on the surface,
to complete instrument deployment
covered by a protective lid to shield
should take about 10 weeks.
it from wind and temperature
Being set on the ground is
changes.
only step one for deploying HP3.
The Heat Flow and Physical
Next, its "mole" has to burrow
Properties Probe (HP3) will peninto Mars. The mole is a cylinder
27 millimeters (about an inch) in
etrate deeply into the ground to
diameter and 40 centimeters (16
escape the wide temperature swings
inches) long, with a pointed tip
on the surface and to measure how
and a tether that connects it to
fast heat is escaping from the Marthe instrument's main package on
tian interior, as well as how the
the surface. Inside are two springsubsurface temperature responds to
loaded weights that can wind up
changing seasons.
p NOISE-CANCELING DOME This tent-like shield will
and hammer in a two-stroke cycle
And in the Rotation and Interior
ensure that Insight's SEIS instrument (seen at bottom)
to bang the mole into the ground -
Structure Experiment (RISE), radio
is protected from seismic "noise" generated by Martian
winds and wide temperature fluctuations.
roughly 1 mm at a time.
dishes on Earth will use their conAll this hammering (an estinection with Insight's transmitter
mated 5,000 to 20,000 hits) will be easily detectable by SEIS.
to measure minute wobbles in Mars's motion that are conseIt will not only sense the taps transmitted directly through
quences of the layering deep within the planet.
the soil but perhaps also the echoes that bounce off geologic
A fourth instrument package, the Auxiliary Payload
layers or large rocks within the soil beneath the lander.
Sensor Subsystem (APSS), is technically a subcomponent of
After every 50 cm (20 inches) that the mole penetrates,
SEIS. It's a suite of meteorology sensors and a magnetomit will stop to "rest." To get accurate data on how heat ﬂows
eter intended to help remove weather effects from the SEIS
within the Martian soil, mission scientists must wait about
measurements. But there'll be scientiﬁc value in the APSS
4 days for the heat generated by drilling to dissipate. Then
observations, too - for example, by comparing the weather
they'll use tiny heaters inside the mole to inject a known
at Insight's landing site with that measured by Curiosity
amount of heat into the soil, and the temperature sensors on
(using nearly identical instruments) in the deep hole of
its tether will record how that heat pulse propagates upward.
Gale crater just 600 kilometers away.
The mole will repeat this burrow-rest-heat cycle until
NASA scientists typically place their landers in geologieither it has penetrated 5 meters deep or its downward
cally interesting settings. But not so with Insight. Flat terrain
is the simplest possible shape to simulate in computational
models of heat ﬂow and earthquake waves. So Insight's team
deliberately picked a landing site that's as dull as possible, ﬂat
and bland in every direction. It also had to be near the equator, to maximize the sunlight falling on the lander's solar-cell
arrays. The winning candidate is a spot in western Elysium
Planitia at 4.5° north latitude and 135.9° east longitude.

M A RS
RS: N ASA / JPL; DO ME: CNES / EM M A NUEL G RIM AULT;
INSIG H T: N ASA / JPL / LOCK HEED M A RTIN
IN

Readying for Work
Assuming that Insight lands without incident on November
26th, its ﬁrst task will be reconnaissance. For three weeks,
the camera on its arm (a spare from the Curiosity mission,
refurbished with a color detector) will methodically survey
the landing site, while the weather package begins routine
monitoring. Insight has one other camera, likewise repurposed from Curiosity and refurbished to capture color, to
provide a ﬁsh-eye view of the workspace within reach of
Insight's robotic arm.
With the help of those early images, the science and engineering teams will choose where to place the seismometer and
heat probe. Then they'll use the robotic arm to lift and place
SEIS, its cover, and HP3 on the ground. The arm has a grapple
at the end of a short cable that will snare specially designed
hooks on these three packages. All of these activities must be

p PROVEN DESIGN Shown during testing in 2015, Insight inherited its
structure and many of its components from the Phoenix lander, which
Lockheed Martin likewise built for NASA.
sk yandtelescope.com * DECE MBE R 2 018

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Sky & Telescope - December 2018

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