Astronomy – October 2019

WTS/SEIS

IDA

IDC

Grapple TWINS

RISE antenna

ICC

RISE antenna

Heat flow probe

TWINS

UHF antenna

HP^3

WWW.ASTRONOMY.COM 23

north of Los Angeles and set InSight on

its way to Mars.

Doing the dirty work

The InSight lander carries two cameras

— one mounted below the deck and the

other on the robotic arm — three main

sets of geophysical experiments, and one

set of meteorological instruments. The

geophysical experiments include the

CNES-led seismometer package called

the Seismic Experiment for Interior

Structure (SEIS). The science team

designed it to detect potential mars-

quakes with up to 300 times the sensitiv-

ity of typical terrestrial seismometers,

and to measure the strength of the

magnetic field at Mars’ surface.

The German Aerospace Center built

the Heat Flow and Physical Properties

Package (HP^3 ), which will measure the

planet’s heat flow and conductivity by

hammering a small probe nicknamed

“the mole” as deep as 16 feet (5 meters)

into the subsurface. The JPL-led radio

transmitter experiment, called the

Rotation and Interior Structure

Experiment (RISE), will improve upon

the experiments on previous landers that

helped deduce the nature of the planet’s

interior, including the size of the core.

The Temperature and Winds for InSight

(TWINS) meteorology package consists

of several temperature, pressure, wind

speed, and wind direction sensors placed

at various heights on the lander.

In addition, the lander carries a pas-

sive retroref lector that will allow future

Mars orbiters to shoot laser beams at the

device and accurately track their range to

the surface. Apollo astronauts left similar

devices on the Moon that let scientists

precisely monitor the distance between

Earth and its satellite. Finally, the probe

carries two tiny silicon wafer chips upon

which NASA microscopically etched the

names of more than 2.4 million people

who signed up to have their names sent

to Mars.

During the years prior to launch, the

InSight science and engineering team

worked to identify the perfect landing

site for the mission. This team’s idea of

perfection differed greatly from that of

most previous mission teams, however.

The InSight seismometers and other geo-

physical instruments need to be in good

contact with the planet’s solid surface to

sense seismic waves and to measure heat

f low accurately. This meant avoiding

rocks, loose sand, and piles of dust.

In addition, the heat shield-parachute-

retrorocket landing system, inherited

from the Phoenix lander, did not have

the sophisticated obstacle-avoidance sys-

tems that have allowed other missions to

target specific small areas. In fact, the

mission’s landing ellipse — the region

of uncertainty where the spacecraft was

most likely to set down — stretched a

robust 81 by 17 miles (130 by 27 kilome-

ters). Compare that with the Curiosity

LEFT: InSight’s Instrument Context Camera (ICC), which is mounted below the lander deck, snapped the

probe’s first image of Mars within hours of landing November 26, 2018. The camera’s transparent lens cover

was still in place to protect the lens from dust kicked up during the landing.

RIGHT: InSight flipped open the lens cover on its ICC on November 30. Although some dust still clings to the

lens, this much clearer view reveals a nearby rock at bottom center as well as one of the spacecraft’s foot-

pads at bottom right. The camera’s fisheye lens creates the curved horizon.

Once InSight gets fully

deployed, its instrument

array should look like

this. As of early July, a

problem has kept the

heat flow probe from

reaching its target

depth. See text for

instrument details.

ASTRONOMY: ROEN KELLY,

AFTER NASA/JPL-CALTECH