Approved and projected probe mission strategies for the outer planet exploration programs are briefly outlined

Herman, D.

English

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N75
KEYNOTE ADDRESS
MR. DANIEL HERMAN - NASA HEADQUARTERS
20359
MR. HERMAN: I am not really going to give a keynote ad-
dress in the formal sense of the word. Rather, what I thought
I would do is to tell you what the current status within NASA
is for an outer planets probe program.
I will begin with this first picture (Figure i-i) of the
so-called official NASA mission model as of last October. These
are the missions Dr. Fletcher presented to the Congress in his
testimony in October and have been carried on the books as the
official NASA plan. Currently, this plan is in the process of
being changed because our thinking with respect to the outer
planet probe missions has changed. I will indicate the changes
from this so-called official NASA mission model of last October
to our current thinking.
Originally, the outer planet probe missions in our plan
were those stipulated by the Outer Planet Science Advisory Group,
headed by Jim Van Allen. The so-called "three to make two"
concept where in three opportunities dedicated Pioneer probe mis-
sions are launched to Saturn and Uranus, with the last one to
either Saturn, Uranus or Titan as a function of the success or
failure of the two predecessors. This strategy of the "October
plan" is shown on the second schedule (Figure 1-2).
In 1979, we would send a dedicated Uranus probe mission to
fly by Jupiter and be deflected to Uranus. The arrival at Uranus
would be 1984. Then, in the 1980 opportunity, we would send a
probe to Saturn directly and that probe would reach Saturn in 1984.
Then in 1981, we would launch a probe mission, the Saturn-Uranus
swing-by opportunity, whichwould reach Saturn in 1985 after both
earlier probes had encountered Saturn and Uranus. If both earlier
Editor's Note: Mr. Herman's remarks accurately reflect the program-
matic and fi-----_scalsituation at the time of the workshop. Subsequent
changes in available resources and other programmatic considera-
tions may alter the mission schedule described in his remarks.
I-3
https://ntrs.nasa.gov/search.jsp?R=19750012287 2020-03-19T20:52:13+00:00Z
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probes were successful, this probe would then go into Titan. If
either the Saturn or Uranus probe was a failure, then this probe
would repeat either the Saturn or the Uranus mission.
The scenario had a couple of weaknesses in it, the major one
of which was exposed at the Titan workshop held here at Ames about
a year or so ago. The strong advice of that workshop, which we
have accepted, was we should not try to achieve commonality be-
tween a Titan probe and an outer planet high-atmosphere probe;
the reasons being that the science to be performed at Titan would
be different and, also, that the quarantine restraints to be im-
posed on a Titan probe would differ from the outer planets probe.
In this old plan (Figure 1-2) you don't see a Jupiter entry
because until the Pioneer I0 encounter our entry analysis of the
Jupiter probe mission, indicated that facilities would not be
available until about 1980 to test an entry probe to the Jupiter
entry heating conditions. Hence, we deferred a Jupiter entry
probe until the mid-1980's. That thinking has changed and that
is going to be a major issue of this workshop.
Let me go tothisnext schedule (Figure 1-3), and show you our
current thinking. For the October mission model we were given a
fiscal constraint by the Administrator to formulate all of the
new programs we hoped to implement for the next five years. The
original mission model was in consonance with that fiscal con-
straint. However, late last year several things happened, one
of which was a forecast overrun in the Viking program.
Since our overall budget does not increase, funds for plan-
ning for new missions is from the same funding that has to ac-
commodate overruns. We, therefore, had to alter our thinking
and decide which missions we wanted to do as scheduled and which
missions would have to be deferred. Since the outer planet probe
missions could be done almost in any year - the opportunities to
the outer planets occur in about a twelve-or fifteen-month period
- these were more easily deferrable than some of our other missions.
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Consequently, when we formulated tha£ mission model, the
dedicated Pioneer outer planet probe missions were deferred. As
I indicated before, our thinking changed about commonality between
an outer planet entry probe and the Titan entry probe and, also with
Pioneer i0 encounter andArv Kliore's data about the possibility that
the probe design for Saturn and Uranus would also have Jupiter capa-
bility. Since ephemeris uncertainty of Jupiter has been decreased
which allows a shallow entry angle, and if the atmosphere is more
toward the so-called'Warm expanded"or"nominal"atmosphere, it may
be possible to enter Jupiter with the same entry technology that
we will use for Saturn and Uranus.
So, for several reasons, our thinking has changed. We have
given up the dedicated Pioneer-Uranus entry probe. Instead, our
current thinking is to incorporate a Uranus probe in a Mariner
Jupiter-Uranus mission which we want to launch in 1979. As far as
a Jupiter entry probe is concerned, we are discussing a cooperative
program with ESRO at the present time, using Pioneer H to do an
orbiter mission in the 1980 opportunity and we are going to dis-
cuss the possibility and the advisability of incorporating a Jupiter
entry probe in that mission.
Our dedicated Pioneer-Saturn probes are still intact. That
thinking has not changed but now you see Pioneer-Saturn-Titan
probes. These would be a different kind of a probe. They would
be dedicated Titan entry missions. The Pioneer-Jupiter probes
is still kept on the books at the old date in case we cannot in-
corporate the probe into the Pioneer Jupiter orbiter mission with
ESRO.
These are some concepts and some of the things that we are
considering. The only way the concept of a probe on the MJU
flyby is feasible is to first aim the spacecraft so that it would
impact Uranus and then release the probe. The probe then need
not have an attitude control system or delta-V propulsion, and
after the probe is released, the spacecraft is deflected to achieve
I-8
the flyby. This mode permits use of a simple, "dumb," probe that
can be developed within reasonable cost and weight constraints.
However, the spacecraft deflection mode requires a new NASA pol-
icy position on the quarantine requirements for outer planet entry
probes. This is being considered by the Space Science Board.
This issue must be addressed since this is the only practical
mode to incorporate a probe on a Mariner spacecraft to Uranus.
Figure 1-4 presents a concept of a dedicated Pioneer probe
mission into Saturn. Again, the concept for probe release would
be the same. The spacecraft, of course, serves as a communica-
tions relay for the probe during the entry of the probe into the
atmosphere. One of the things that is being studied is the fea-
sibility of designing one probe system which can be completely
common, including science for both Saturn and Uranus.
A cooperative Jupiter mission with ESRO that I mentioned,
and the possibility of a•probe in that is shown here on Figure
1-5. The probe would be released before orbit capture and the
spacecraft would serve as a relay for the probe during entry.
Then the spacecraft would be captured and would achieve a highly
elliptical orbit about the planet. The first formal meeting with
ESRO on this mission is here at Ames on June 17 and 18.
Now, let me tell you one announcement that I think will be
of interest to some people here. The Mariner Jupiter-Uranus
Science Group that has been meeting is coming up with a strong
position that an atmospheric entry probe will materially enhance
the value of that mission. On the basis of a meeting last week,
we at NASA decided that we would go out with an RFP to industry
for a Phase B Study in fiscal year 1976 for an entry probe that
can be used for Uranus, Saturn and, if possible, Jupiter. The
RFP will be entitled, "Outer Planet Probes." The RFP will also
state that the first mission for this outer planet probe family
will be the MJU mission in 1979. Preceding the release of that
RFP, Dr. Rasool is going to form a small science group to evaluate
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the payload that should be incorporated _the probe and this
will serve as a guideline for the Phase B contractors.
Our current thinking is that this RFP, which would be com-
petitive, would be released about July of next year and the pro-
curement procedure would be similar to Pioneer-Venus. It would
be open competition with two contractors selected to conduct a
competitive Phase B and only the winners of the Phase B allowed
to compete for the execution phase.
1-12
SESSION II. SCIENCE RATIONALE AND OBJECTIVES
Dr. Ichtiaque Rasool, Chairman
MR. SEIFF: I think everybody knows Ichtiaque Rasool who
is the Deputy Director in the Planetary P_ograms Office in OSS.
Prior to that he was working at Goddard and at the Goddard
Institute for Space Studies. He has been of great service to
the planetary programs at some professional sacrifice to himself
because he has had to giveup some of his scientific work in
order to help advance the programmatic aspects of these projects.
Dr. Rasool has kindly agreed to ser_e as chairman of this session.
DR. ICHTIAQUE RASOOL: Thank you
Now we come to the most important part of the session.
As you know, the planetary program is having great success at
the moment; technology wise and science wise, we have done
very well.
Last week I was asked by my boss, John Naugle, "Why?" Why
are we having such great success? It is very interesting that
when we have a failure, we have an inquiry; and when we are
having success, we still have an inquiry. But it isan inter-
esting question, why our program, compared to many other pro -
grams in other countries, has had great success in the ten
years NASA has been in the planetary business.
I have reflected on that quite a bit in the last few days
and I think very firmly that the main reason has been the strong
base of supporting planetary technology and advance planning.
We go through a great deal of research and technology develop-
ment and we do very careful planning. We go through a great
amount of technical development and technical studies. A very
important thing is that we have conducted science and technology
studies together. I think this mix is extremely important. We
design our missions to answer specific questions. This, in the
next ten or fifteen years, is going to be very important be-
cause now we are entering the second generation of planetary
II-i
exploration. The first generation was to go and find out what
is there and now we know a little bit of what is there on the
terrestrial planets, and through very powerful telescopes we
have been looking atthe outer planets.
Once we know what is there, then the question is why is
it there and what does it mean in terms of the history of the
solar system? So our major objective is that we would like to
understand the processes which took place in the early history
of the solar system, what is the history of the Earth and what
may we estimate to be the future of the Earth. Those are the
specific questions and it is to those questions that our space-
craft design and mission design should be geared to answer. That
is the interaction of science and technology. That is what we have
been doing and in my opinion that is why our program has been sci-
entifically very productive.
It's very appropriate then that our first session be a
definition of science. We have six or seven Speakers who will
start with a general discussion of what we know about the outer
planets. In this last ten or fifteen years we have concentrated
on the inner planets and we have used flybys and orbiters. The
next decade will be the outer-planet era, hopefully, and there
the emphasis will be on flybys, orbiters and probes. As you
know, the structure of the outer planets is very different from
the inner planets and, therefore, it is very important that we
begin this historic meeting - which I think is a very good way
to kickoff the 1980's at which time probe technology will be the
word of the day - by trying to find out what is there, why are
we going there, what do we expect to learn, and what measurements
do we need to make.
The first paper is a general review of what we know
about the outer planets by Toby Owen. I have asked him to in-
clude Titan in his paper because he has become very interested
in Titan in the past few months.
II-2


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