186
Carl Wunsch
which NASA was looking for things to do. A committee of enthusiasts had been put
together by NASA that proposed an ocean satellite to measure virtually everything
from space that seemed technically possible, in some cases without much justification for what the measurement would say about the ocean. As part of the Bender
Committee, I undertook to read the documentation justifying the decision that had
already been made to fly SEASAT-A. (One question we were faced with was how a
successor satellite—SEASAT-B—should be configured; it was taken for granted that
there would be a follow-on of some sort.) The level of technical detail and justification for SEASAT-A in the reports would be regarded as extremely thin, bordering
on the laughable, by today’s standards. As I read through the documents, however, I
finally came to the discussion of the altimeter that would be on the satellite. Although
the report said little about how the measurements would be used, it became clear to
me that if the instrument system could live up to the engineering specifications, it
represented a very exciting possibility—the measurement of surface dynamic height
from space at a useful level of accuracy. From the earliest days of the so-called dynamic method, about 1900, the direct determination of sea surface slopes relative to
a reference surface (called the geoid) had been recognized as an important concept,
but whose measurement was regarded as essentially impossible. Here was NASA
explaining, in primarily engineering terminology, that perhaps it could be done. I got
interested.
SEASAT (the “A” was dropped on launch) finally flew in 1978, but instead of
running for several years, it failed after three months. (Rumors immediately circulated
that it had been deliberately killed by the U.S. Air Force, who were supposed to have
aimed a laser at it. In the aftermath of the Vietnam War, many scientists were deeply
suspicious of the military, and there indeed had been great tension over whether
the SEASAT measurements would be classified. The SEASAT saga remains to be
written.) As it turned out, the failure after so short a time was something of a blessing.
Cost overruns on the hardware and launch had eaten up the science analysis budget.
With the failure, some money from the operations budget was made available to the
science community to analyze what data there were. These proved adequate to show
that the altimeter actually worked at the levels of accuracy and precision predicted
by the engineers. For example, one could clearly see the Gulf Stream and associated
rings (Wunsch and Gaposchkin, 1980; Cheney, 1982). The concept had been proven
(see Figure 12.1).
A separate (long) paper would be required to describe the events that ultimately
led to the launch of what is now known as TOPEX/POSEIDON, a U.S.–French mission that became the centerpiece of WOCE. Anyone who becomes involved with
the formulation of a new mission will have their own stories of near-failure, bureaucratic and political craziness, heroic and not-so-heroic individuals, and plain luck.
That TOPEX/POSEIDON was actually launched, and has performed far beyond its
specifications for, as I write, almost 13 years (the agreed lifetime was 3–5 years)
is in the nature of an engineering/scientific/political miracle that deserves its own
history.
Carl Wunsch
which NASA was looking for things to do. A committee of enthusiasts had been put
together by NASA that proposed an ocean satellite to measure virtually everything
from space that seemed technically possible, in some cases without much justification for what the measurement would say about the ocean. As part of the Bender
Committee, I undertook to read the documentation justifying the decision that had
already been made to fly SEASAT-A. (One question we were faced with was how a
successor satellite—SEASAT-B—should be configured; it was taken for granted that
there would be a follow-on of some sort.) The level of technical detail and justification for SEASAT-A in the reports would be regarded as extremely thin, bordering
on the laughable, by today’s standards. As I read through the documents, however, I
finally came to the discussion of the altimeter that would be on the satellite. Although
the report said little about how the measurements would be used, it became clear to
me that if the instrument system could live up to the engineering specifications, it
represented a very exciting possibility—the measurement of surface dynamic height
from space at a useful level of accuracy. From the earliest days of the so-called dynamic method, about 1900, the direct determination of sea surface slopes relative to
a reference surface (called the geoid) had been recognized as an important concept,
but whose measurement was regarded as essentially impossible. Here was NASA
explaining, in primarily engineering terminology, that perhaps it could be done. I got
interested.
SEASAT (the “A” was dropped on launch) finally flew in 1978, but instead of
running for several years, it failed after three months. (Rumors immediately circulated
that it had been deliberately killed by the U.S. Air Force, who were supposed to have
aimed a laser at it. In the aftermath of the Vietnam War, many scientists were deeply
suspicious of the military, and there indeed had been great tension over whether
the SEASAT measurements would be classified. The SEASAT saga remains to be
written.) As it turned out, the failure after so short a time was something of a blessing.
Cost overruns on the hardware and launch had eaten up the science analysis budget.
With the failure, some money from the operations budget was made available to the
science community to analyze what data there were. These proved adequate to show
that the altimeter actually worked at the levels of accuracy and precision predicted
by the engineers. For example, one could clearly see the Gulf Stream and associated
rings (Wunsch and Gaposchkin, 1980; Cheney, 1982). The concept had been proven
(see Figure 12.1).
A separate (long) paper would be required to describe the events that ultimately
led to the launch of what is now known as TOPEX/POSEIDON, a U.S.–French mission that became the centerpiece of WOCE. Anyone who becomes involved with
the formulation of a new mission will have their own stories of near-failure, bureaucratic and political craziness, heroic and not-so-heroic individuals, and plain luck.
That TOPEX/POSEIDON was actually launched, and has performed far beyond its
specifications for, as I write, almost 13 years (the agreed lifetime was 3–5 years)
is in the nature of an engineering/scientific/political miracle that deserves its own
history.