[meteorite-list] HiRISE: 45,000 Mars Orbits and Counting
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 24 Mar 2016 16:48:33 -0700 (PDT)
HiRISE: 45,000 Mars Orbits and Counting
University of Arizona
March 23, 2016
Ten years ago on March 24, the UA-built camera began taking the most detailed
images of the Martian surface to date. Since then, the camera has become
the world's eye on Mars, bringing us detailed vistas of landscapes ranging
from strangely alien to earthly familiar.
On March 24, 2006, the UA-led High Resolution Imaging Science Experiment,
or HiRISE, snapped its first test image, showing the Martian surface in
unprecedented detail and beauty. The scene covers an area about 31 miles
long and 15 miles wide of landscape typical of Mars' mid-latitude southern
highlands. (NASA/JPL-Caltech/University of Arizona)
True to its purpose, NASA's Mars Reconnaissance Orbiter, or MRO, the spacecraft
that began orbiting Mars a decade ago, has delivered huge advances in
knowledge about the Red Planet.
According to NASA's Jet Propulsion Laboratory, MRO has revealed in unprecedented
detail a planet that held diverse wet environments billions of years ago
and remains dynamic today. MRO carries, among other instruments, the High
Resolution Imaging Science Experiment, or HiRISE, camera, designed and
operated by the Lunar and Planetary Lab at the University of Arizona.
One example of the orbiter's major discoveries was published last year,
about the possibility of liquid water being present seasonally on present-day
Mars. It drew on three key capabilities researchers gained from this mission:
telescopic camera resolution, to find features narrower than a sidewalk;
spacecraft longevity, to track seasonal changes over several Martian years;
and imaging spectroscopy, to map surface composition.
"Our views of both ancient and modern Mars have changed dramatically in
the past decade," says Alfred McEwen, principal investigator of HiRISE.
"Now we know that hydrated minerals are common in ancient bedrock, many
sand dunes are active, that carbon dioxide frost rather than water is
carving gullies, and there is water in other seasonal flows."
Other discoveries have resulted from additional capabilities of the orbiter.
These include identifying underground geologic structures, scanning atmospheric
layers and observing the entire planet's weather daily. All six of the
orbiter's science instruments remain productive in an extended mission
more than seven years after completion of the mission's originally planned
primary science phase.
The Arrival at Mars
On March 10, 2006, the spacecraft fired its six largest rocket engines
for about 27 minutes, slowing it down enough for the gravity of Mars to
catch it into orbit. Those engines had been used only once before, for
15 seconds during the first trajectory adjustment in the seven-month flight
from Earth to Mars.
For its first three weeks at Mars, the spacecraft flew elongated, 35-hour
orbits ranging as far as 27,000 miles from the Red Planet. During the
next six months, a process called aerobraking used hundreds of carefully
calculated dips into the top of the Martian atmosphere to gradually adjust
the size of the orbit. Since September 2006, the craft has been flying
nearly circular orbits lasting about two hours, at altitudes from 155
to 196 miles.
The spacecraft's two large solar panels give MRO a wingspan the length
of a school bus. That surface area helped with atmospheric drag during
aerobraking and still cranks out about 2,000 watts of electricity when
the panels face the sun. Generous power enables the spacecraft to transmit
a torrent of data through its main antenna, a dish 10 feet in diameter.
The total science data sent to Earth from MRO ??? 264 terabits ??? is
more than all other interplanetary missions combined, past and present.
"The HiRISE team at the UA developed routines to automatically process
the raw data into beautiful images, within hours of when the data is returned,"
Lockheed Martin Space Systems of Denver built the spacecraft with the
capability to transmit copious data to suit the science goals of revealing
Mars in great detail.
For example, the HiRISE camera has returned images that show features
as small as a desk anywhere in observations that now have covered about
2.4 percent of the Martian surface, an area equivalent to two Alaskas,
with many locations imaged repeatedly. The Context Camera, or CTX, managed
by Malin Space Systems of San Diego, has imaged more than 85 percent of
Mars, with resolution showing features smaller than a tennis court. The
Compact Reconnaissance Imaging Spectrometer, or CRISM, built and operated
by Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland,
also has imaged nearly 80 percent of the planet in multiple visual-light
and infrared wavelengths, providing composition information at scales
of 100 to 200 yards per pixel.
Data from MRO has improved knowledge about three distinct periods on Mars.
Observations of the oldest surfaces on the planet show that diverse types
of watery environments existed, some more favorable for life than others.
More recently, water cycled as a gas between polar ice deposits and lower-latitude
deposits of ice and snow, generating patterns of layering linked to cyclical
changes similar to ice ages on Earth.
Watching Mars Change
Dynamic activity on today's Mars includes impact events, avalanches, dust
storms, seasonal freezing and thawing of carbon dioxide sheets, gully
formation, sand migration and summertime seeps of brine.
"This mission has helped us appreciate how much Mars ??? a planet that
has changed greatly over time ??? continues to change today," said MRO
project scientist Rich Zurek of JPL in Pasadena, California, which manages
MRO provides three types of crucial support for rover and stationary lander
missions to Mars. Its observations enable careful evaluation of potential
landing sites. They also help rover teams choose routes and destinations.
Together with NASA's Mars Odyssey, which has been orbiting Mars since
2001, MRO relays data from robots on Mars' surface to NASA Deep Space
Network antennas on Earth, multiplying the productivity of the surface
Recently, the mission has begun investigating areas proposed as landing
sites for future human missions in NASA's Journey to Mars.
"The Mars Reconnaissance Orbiter remains a powerful asset for studying
the Red Planet, with its six instruments all continuing capably a decade
after orbit insertion," Zurek said. "All this and the valuable infrastructure
support that it provides for other Mars missions, present and future,
make MRO a keystone of the current Mars Exploration Program."
Just this week, another orbiter blasted off the Earth, slated to join
MRO in orbit around Mars by mid-October: The ExoMars Trace Gas Orbiter,
or TGO, a collaboration project of the European Space Agency, or ESA,
and Russia's Roscosmos State Space Corporation. The UA's HiRISE team is
supporting the Colour and Stereo Surface Imaging System, or CaSSIS, for
science planning software development, data processing and science analysis.
NASA's Jet Propulsion Laboratory contributed to this story.
Received on Thu 24 Mar 2016 07:48:33 PM PDT