Voyager 1 took this photo of Jupiter and two of its satellites (Io, left, and
Europa) on Feb. 13, 1979. Io is about 350,000 kilometers (220,000
miles) above Jupiter’s Great Red Spot; Europa is about 600,000
kilometers (375,000 miles) above Jupiter’s clouds. Credit: NASA/JPL
not place impossible demands on the other teams,
while still ensuring that the spacecraft would be
active enough to meet the scientists’ desires.
“For example: the encounter period for Jupiter
is going to start at minus 80 days and end at plus
30 days. It’s going to be divided into three basic
phases, such as far encounter, near encounter, and
post encounter. Each phase will have a defined
duration and prescribed number of sequence loads;
this is the number of activities we’ll have; here’s how
much we can afford to sequence, and so on.
“So, once we launched in ‘77 my job as Mission
Planning Office Manager was balancing all this.
I had a small office and group of people, but all
well-chosen. I had a chance at various times to get
off the project. I could have left after Saturn, but it
was too exciting, the spacecraft were working, we
were making constant and amazing discoveries,
and we were going to Uranus and Neptune.”
RS: The two spacecrafts’ cameras returned so many
stunning and iconic images of these beautiful and
strange worlds. Do you have a favourite image?
KOHLHASE: “It’s impossible to pick a favourite, but
one image has a special meaning for me. It’s one
taken by Voyager 1 several days out from Jupiter,
showing Io and Europa in front of the Jovian disk. We
were beginning to see detail on the surface of these
Galilean satellites and they were beginning to look
like their own fascinating worlds - we were seeing new
worlds up close for the first time in human history.”
RS: How did your role on Voyager change after launch?
KOHLHASE: “In theory, and I’m always grateful to Casani
for this (Note: John Casani, Voyager Project Manager,
Prelaunch Phase), once the Voyagers were launched I
probably could have and should have gone to another
project, but John said ‘We’d like you to stay aboard,
not as the Mission Analysis and Engineering Manager’,
which is what I’d been for nearly 4 years, ‘but as the
Mission Planning Manager to decide how much we
could afford to do at each planet’. Here we have
these two spacecraft with limited memory capacity. To
programme them to do scientific observations requires
manpower. There are constraints - we don’t want to
put demands on the Deep Space Network which they
can’t meet, we want to make sure we’re not trying to
send commands during occultations, and so on. Casani
said, ‘We also want you to limit the size of the computercontrolled scientific observation sequences, so that
the sequence team has the time to build and carefully
check each sequence load.’ During the mission you
send a load up and the spacecraft executes for several
days, then you send another load up, and so on.
“So, my office basically took each encounter
and produced in advance the mission planning
guidelines and constraints that would be planned
for and executed '