the mission-spacecraft interactions, writing the reports
and putting the requirements on the launch vehicles.”
RS: From the science point of view, what were
the reactions to the first images sent back from
Mars in 1964, which showed a cratered world?
KOHLHASE: “Well, the early Mariners seemed to show
Mars as a cratered, somewhat uninteresting place.
Mariner 7’s instruments did image the edge of the
southern polar cap, showing frost or ice, but Mars
did not emerge as a really interesting world until the
first successful orbiter, Mariner-71 (Mariner 9), which
arrived in November 1971. We had to ride out a dust
storm for a couple of months, but then the complexity
of the surface and its atmosphere were revealed.
“I myself didn’t work on Mariner-71. I jumped to Viking
after the Mariner-69 missions. I was the Navigation
Development Team Leader for Viking, but now also got
more into the overall mission design, so I was writing
mission requirements and documents on all the systems.
In fact, I co-authored a high-level document referred to
as the ‘Mrs. D’ - Mission Requirements on System Design.”
RS: When was the decision made to mount the
Viking mission and how did it come about?
KOHLHASE: “There was a desire to go to Mars on a
project initially called Voyager, believe it or not. It was
planned between 1966 and 1968 as part of the Apollo
Applications Program, and was scheduled for launch in
1974–75. It was very risky. We were going to use a Saturn
C5, the biggest launch vehicle in the US, and put two
complete orbiter-lander missions on a single launch.
They were firstly conceived as precursors for a manned
A boulder-strewn field of red rocks stretches across the horizon in this self-portrait
of Viking 2 on Mars’ Utopian Plain. Credit: NASA/JPL
landing on Mars in the 1980s. Then NASA realised that
we’d have all our eggs in one basket, which would be
a mistake, so that was cancelled. And Viking arose in
its place in 1968, led by Project Manager James Martin,
former assistant manager for the Lunar Orbiter Project.
It separated the missions on different launch vehicles.
“Viking was very interesting work. It was an
expensive, challenging mission run out of Langley
Research Centre. Martin Marietta of Denver was
building the lander and JPL was building the orbiter.
“Now, I had a hard decision to make in 1974. I
could stay with Viking and become the Navigation
Team Leader for operations, or I could
get on this great Voyager mission, where
the planets only line up every 176 years.
This would give me the chance to work
with Bud Schurmeier again, with whom
I’d worked on Mars ‘69. So, I left Viking in
late 1974, even though it was an activelyfunded project, and moved to Voyager
and loved every minute of it! I did worry at
first about whether I was capable enough
to do the job, and I had some sleepless
nights. But I had developed enough of the
fundamentals of mission design, navigation
and spacecraft performance to handle it.”
RS: At that stage, you were writing
the rule books and procedures
as the missions evolved.
Image from the computer animation of the Voyager Saturn encounter, created by Blinn and
Kohlhase, which was so important for public outreach for the missions. Credit: Charles Kohlhase
KOHLHASE: “Yes, with Schurmeier
looking over my shoulder initially,
but he began to trust me and soon
I was off on my own, generating the
requirements and procedures on the
project and mission systems for Ed
Stone (Voyager Project Scientist) and
the science team from then on.”
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