Emily Lakdawalla
Page 8
48 Green (2009)
49 Woerner et al (2013)
50 Manning and Simon (2014)
40 Mars Science Laboratory
Figure 1.15. Panoramic view of the High Bay on March 16, 2009. The MSL hardware has been mothballed, and not an engineer is in sight. Photo by Emily Lakdawalla.
When I was younger, I wondered, ‘Why is the sky blue?’, ‘Why do the stars twin-
kle?’, ‘Why am I me?’, and I still do. I had so many questions, and America is the
place where I want to find my answers. Curiosity is the passion that drives us through
our everyday lives. We have become explorers and scientists with our need to ask
questions and to wonder. Sure, there are many risks and dangers, but despite that, we
still continue to wonder and dream and create and hope. We have discovered so
much about the world, but still so little. We will never know everything there is to
know, but with our burning curiosity, we have learned so much.
1.6.3 Problem solving
With schedule pressure reduced, the sample handling team added elements to deal with the
concerns raised by Phoenix’ problems handling samples. They mounted prongs and other
tools to the front of the rover to allow it to poke out stubborn gunk, and a “sample playground”
with a tray, funnel, and other devices where they could dump sample for visual inspection (see
section 5.7). They added wind baffles around the sample inlets and across the sample portioning device. They modified the sample portioner from a straight tube to an inverted funnel
shape, to make sure sample material would not get stuck as it had on Phoenix.51
51 Louise Jandura and Cambria Hanson, personal communication, interview dated June 3, 2016
1.6 A Two-Year Respite (2009–2010) 41
The avionics team started over with one particularly challenging bit of the computer
design: the asymmetric cross-strapping between the redundant main computers. They
reduced the asymmetries, making the complex system slightly easier to understand and
more straightforward to test. 52
Data on the final four landing sites poured in from the three Mars orbiters. The United
States Geological Survey used overlapping pairs of high-resolution images to develop
highly detailed digital terrain models of large swaths of the landing ellipses. Engineer
Paolo Bellutta took algorithms developed for the Mars Exploration Rovers and applied
them to the digital terrain models, making maps of the “traversability” of the terrain and
estimating drive times to reach likely science targets from likely landing spots.
The delay permitted the team to solve ChemCam’s operational problems as well.
Thermal engineers designed a thermo-electric cooler that could be incorporated into the
ChemCam body unit and used to cool its detectors (see section 9.2.1.2). ChemCam’s spectrometers and housing had originally been built out of beryllium and magnesium rather
than aluminum in order to save mass, but now mass wasn’t a factor. The addition of the
coolers doubled ChemCam’s mass. 53 The end result was that ChemCam could actually be operated at almost any time of day, except for the hottest parts of summer afternoons.
The landing engineers worked on fiddly details of the order of events during landing,
finding ways to shave off risk here and there. For example, after spending time with mod-
els and empirical tests of mobility system deployment, they shifted the event until quite
late in the landing sequence, during the sky crane phase. Figure 1.16 depicts the entry, descent, and landing sequence in its final form.
Engineers on the landing team performed simulation after simulation, testing their
landing system against a huge variety of landing-day scenarios, increasing their confi-
dence in their system.
A fourth landing site selection workshop took place on September 27, 2010, to discuss
the merits of the final four sites in the context of the new scientific results from Mars
Reconnaissance Orbiter. All four sites remained possibilities.
Not all the development news was good. The Department of Energy measured the
power output of the stored MMRTG on a quarterly basis. As of late summer 2009, the
Department of Energy predicted that the MMRTG would be producing 110 watts of power
on landing day, and planning proceeded according to that assumption. But the next mea-
surement, taken in late 2009, revealed that the MMRTG was under-performing. Now they
had two problems: the lower-than-predicted power levels and the mystery of why their
modeling was not working.
Even before the delay, there had been insufficient power to run the rover. The delay
gave them time to address the power problems by replacing the rover’s battery with one
that had double the original capacity. Finding space for the new battery in the cramped
interior of the warm electronics box required them to partially disassemble the rover. But
the battery upgrade gave the rover about 1600 watt-hours of usable capacity, and ensured
that power was rarely a limiting factor in running the rover for any but the most power-
hungry activities, at least during the prime mission. 54
52 Manning (2014)
53 Wiens et al (2012)
54 Manning and Simon (2014)
42 Mars Science Laboratory
Figure 1.16. Schematic diagram of approach, entry, descent, and landing. From the Mars Science Laboratory launch press kit, November 2011. Minor changes from previous diagrams include a very late deployment of the wheels and an emphasis on the lengthy period of near-horizontal flight during the “hypersonic aero-maneuvering” phase.
1.7 FINAL PREPARATIONS (2010–2011)
1.7.1 ATLO, again
The redesigned motors finally began to arrive at JPL in 2009, with the flight models being
delivered in 2010. Assembly of the rover began in June 2010 and proceeded rapidly. The
legs and wheels were attached at the end of June, as was the mast with all its cameras and
ChemCam (Figure 1.17). The rover first spun all six wheels on July 9, and drove on its wheels for the first time on July 23 (Figure 1.18). The arm was attached in August, and put through its paces with the rover sitting at tilts of up to 20° (Figure 1.19).
With the spacecraft finally coming together, systems engineers could begin to test how
all the subsystems functioned together – and make sure that the spacecraft safely handled
problems. Engineers performed a series of system tests, each focused on a different mis-
sion phase. In parallel, engineers took all components of the spacecraft into JPL’s thermal vacuum chamber to perform environmental tests. The chamber simulates the harsh environments of deep space and the Mars surface (Figure 1.20). It can be pumped down to near-vacuum, cooled with liquid nitrogen, and lit with thirty-seven 25,000-watt xenon
lamps to simulate direct solar heating in deep space.55
55 JPL (2010)
1.7 Final Preparations (2010–2011) 43
Figure 1.17. Mobility system installation, 29 June 2010. NASA/JPL-Caltech release PIA13234.
Figure 1.18. The rover’s first drive, 23 July 2010. The corner wheels are steered into position to allow the rover to turn in place. NASA/JPL-Caltech release PIA13308.
44 Mars Science Laboratory
Figure 1.19. Testing out the arm’s positioning from a tilted rover, 16 September 2010. NASA/
JPL-Caltech release PIA13389.
1.7 Final Preparations (2010–2011) 45
Figure 1.20. Thermal vacuum testing. Top: The cruise stage and backshell, August 24, 2010.
Bottom: The rover
during Surface Test 8, March 8, 2011. NASA/JPL-Caltech releases
PIA13359 and PIA13806.
46 Mars Science Laboratory
Despite various hiccups, the tests were mostly successful, demonstrating that the space-
craft could function through entry, descent, and landing, and in surface operational sce-
narios. The final system test, which took place after the spacecraft had been shipped to
Florida, simulated three days of typical science activities on the surface, proving that the flight system was ready for Mars. But only just. The tight schedule and complexity of
interacting systems meant that the system software was not particularly mature.
Public information officers began to stir up public interest in the mission. On June 24,
2011, NASA released a computer animation depicting the launch, cruise, and landing of
the rover. The animation had been directed by JPL visualization artist Doug Ellison and
produced by animator (and former JPL artist) Kevin Lane, who packed the thrilling video
with accurate details of the landing sequence, informed by research and interviews with
engineers (Figure 1.21).
Figure 1.21. The moment of touchdown as depicted in the landing animation. NASA/JPL-Caltech release PIA14840.
1.7 Final Preparations (2010–2011) 47
1.7.2 Going to Gale
The fifth and final community workshop on landing site selection opened on May 16,
2011. Engineers remained confident that their entry, descent, and landing system could
handle any of the four landing sites under discussion. Scientists pored over the data col-
lected by Mars Reconnaissance Orbiter and Mars Express on the four sites and debated the
scientific questions that could be answered at each one. The workshop produced no spe-
cific recommendation, but gave the MSL science team the background they needed to
discuss the merits of the four landing sites at a team meeting on May 18.
Based on the wider community and narrower team discussions, the project science
group (a committee of all of the instrument principal investigators) selected Gale crater as its top choice. In addition to its compelling scientific targets of layered rocks and alluvial fans, it was also the lowest-elevation and most equatorial of the four proposed sites, the
most benign landing case. It had some possibility for science within the landing ellipse,
but most of its science would be on a go-to mission, driving beyond the ellipse to reach
mineral-bearing rocks at the base of the crater’s central mountain (Figure 1.22).
Figure 1.22. Oblique view of Gale crater. The black landing ellipse is 25-by-20 kilometers in extent. The blue line shows a possible route for Curiosity to ascend the mountain. NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS release PIA15292.
The project science group recommended Gale and Eberswalde as potential landing
sites to NASA, preferring Gale. The final decision would be made at NASA Headquarters.
The landing site selection committee gave a presentation to an independent landing site
certification board on June 9 and 10, 2011. The NASA Planetary Protection Office
48 Mars Science Laboratory
reviewed the four sites for compliance with planetary protection provisions on June 23.
The next day, the MSL project presented the four sites to NASA Headquarters representa-
tives, who concurred with the downselection to Eberswalde and Gale. They reconvened a
month later and recommended Gale. NASA announced the selection of Gale crater as
Curiosity’s landing site on July 22, 2011.
1.7.3 Journey to Florida
As Earth crept toward Mars on its inside track around the Sun, the once-every-26-months
launch period approached. NASA had missed the intended window in 2009; they could not
afford to miss the 2011 window. Between May and November 2011, all of the pieces of
the interplanetary spacecraft would come together at Kennedy Space Center in Florida.
On May 12, 2011, a C-17 transport plane carried the heat shield, backshell, and cruise
stage from California to Florida. A scary event happened during processing of the space-
craft on May 20. A crane operator accidentally lifted the backshell and the support cart that the backshell was attached to off of the ground, exerting unplanned loads on the backshell.
There was no obvious damage, but engineers scrambled to figure out whether the weight
of the cart suspended from the backshell could have damaged it. They determined that the
backshell was designed robustly enough to withstand the additional load of the cart, and
assembly could proceed as normal. 56 But the incident ratcheted up the tension on the
launch preparations.
Meanwhile, tests continued on the rover back at JPL at a feverish pace. It was finally
buttoned up and transported to Florida, along with the descent stage, on June 23. The
Department of Energy delivered the MMRTG on June 30. Components of the Atlas V
rocket arrived at Kennedy aboard the Delta Mariner barge a month later.
1.7.4 Planetary protection jeopardy
Problems with the drill bits dogged the mission right up until launch. Early in 2011, the
project discovered that residue from oil used in manufacturing the test drill bits was con-
taminating drilled samples. If there was similar oil on the flight drill bits, it could invalidate SAM’s attempts to search for Martian organic compounds. By March, they had
figured out how to re-manufacture the drill bits, and planned to deliver them just in time
for the rover to be shipped to Florida. 57
The SAM team had to know whether the flight drill bits also carried traces of hydrocar-
bons. In Florida, a team of contamination control engineers opened the sterile bit enclo-
sures to check for the oil residue. They found no contamination – but in checking for oil
contamination, they had broken the sterile seal on the bits, and the bits were not re-
sterilized. Even if they had not checked for the oil contamination, they would have had to
break the sterile containment of one of the bits to install it on the rover, because of a
change in mission plan. Originally, Curiosity was to have launched to Mars with all three
56 NASA Office of Inspector General (2011)
57 Manning and Simon (2014)
1.7 Final Preparations (2010–2011) 49
bits enclosed in sterile boxes, and only break that seal upon arriving at Mars and loading
the first bit in the drill. The mission decided it was too risky to launch without one bit
preloaded. That bit was not in sterile wrapping throughout the rover’s delivery to Florida
and assembly operations, in violation of the mission’s planetary protection plan.
The wheels represented another vector by which Earth microbes could contaminate
Mars. They were heat-sterilized and wrapped to prevent recontamination during final
assembly. But the planetary protection requirements weren’t specific about when it was
permissible to unwrap the wheels, with ambiguous requirements like “The flight wheels
shall be mounted on the rover as late as possible and will be covered as much as possible
to prevent recontamination.” 58 Photos from the Kennedy Space Center show that the wheel wrappings were removed just after delivery, on June 27. The final system tests were performed in July and August with the wheels unwrapped and resting on the floor (Figure 1.23).
They were re-wrapped before the spacecraft was stacked to the descent stage and back-
shell in late September, and the wrappings removed for the final time before heat shield
encapsulation in early October.
Figure 1.23. Engineers at Kennedy Space Center test out the rover’s motor functions, July 18, 2011. NASA/KSC release KSC-2011-5919.
58 NASA Office of Planetary Protection (2014)
50 Mars Science Laboratory
The lack of sterile containment of both wheels and drill bits was “a clear violation” of the mission’s planetary protection requirements.59 The Office of Planetary Protection did not learn of the violation until less than three months before the launch, in mid-September. On September 20, Peter Theisinger formally requested permission to deviate from the requirements, and the Office of Planetary Protection rejected that request. The violation of planetary protection requirements had the potential to jeopardize Curiosity’s on-time launch.
Not enough time remained to remove, sterilize, and replace the drill bits and wheels
before the launch. The only way out was a bureaucratic one: to reclassify the mission to a
lower planetary protection standard. Fortunately, with its low elevation and equatorial
location, Gale crater is a site where no ground ice was expected to be anywhere close to
the surface, so a landing failure had no potential to create a spacecraft-induced special
region (see section 1.4.5). That made it possible to reclassify the mission from planetary protection category IVc down to category IVa, reserved for “lander systems not carrying
instruments for the investigations of extant martian life” that will not come into contact
with any special region.60
Catherine Conley, NASA’s planetary protection officer, formally recategorized the mis-
sion to category IVa on November 1. “Violation of NASA planetary protection require-
ments represents a significant risk to the MSL project,” she wrote in a letter to mission and NASA management. “Requesting a planetary protection deviation of this magnitude, so
late in the project lifecycle, is improper.” She singled out the wheels as representing the greatest risk for contaminating Mars, and imposed restrictions on the rover's future exploration activities:
The project is prohibited from introducing any hardware into a Mars Special Region,