Q1. At the time -- 1978 -- what were the chief motivations for SUSIM? Did it simply represent the next step in a continuous program of solar UV irradiance measurement since Dr. Tousey's original V-2 work in the late '40s and '50s? The grant proposal (for SUSIM aboard UARS, 1978, # 71-051-78-80) cites the need for longer-term measurement possible only from a satellite platform -- a purely scientific need -- but also mentions the ozone problem, a phenomenon with social repercussions. Global temperature variation is, I believe, not mentioned in the grant proposal but is discussed in the SUSIM brochure published c. 1990. Of course, back in 1978 ozone depletion was a current concern, while global warming became so only later.
A1. The chief motivation for SUSIM was to measure the variability of the full-sun ultraviolet spectral irradiance as accurately as possible, by designing SUSIM so that changes in calibration could be tracked while the instrument was in orbit. While the design and development of SUSIM did make use of the experience gained from flying previous space instruments by personnel in what had been Tousey's Solar Physics Branch, SUSIM was NOT "the next step" of that program. That program was directed toward instruments with increasingly higher spectral resolution and/or increasingly higher spatial resolution. (It was the HRTS (High Resolution Telescope and Spectrograph) instrument, which was flown on sounding rockets and was aboard the space shuttle during the 1985 Spacelab-2 mission, that was "the next step", rather than SUSIM, SUSIM having modest spectral resolution by comparison and no spatial resolution at all.)
What caused SUSIM to come into existence was the confluence of: (1) the development (first, by the National Physical Laboratory in England) of radiantly repeatable and stable deuterium discharge (calibration) lamps that could be powered by "typical" electronics then flown in space and that appeared to be capable of surviving launches into space, and (2) the NASA Announcement of Opportunity (AO) for proposing instruments, first for the Space Shuttle, then for the UARS mission. [The NASA AO's were important; scientists at NRL are always on the lookout for future funding sources (because support, even for salaries, is NOT "guaranteed" by NRL). I think Guenter Brueckner, Tousey's successor as Head of the Solar Physics Branch and who became the SUSIM PI, saw the UARS AO as requiring a relatively simple instrument whose development would enable him to keep some of his experienced technical staff into the future. {Here, I'm giving you my impression of what Dr. Brueckner thought; these impressions can't be verified because, I regret to say, Dr. Brueckner died on July 11, 1998.}]
The atmospheric reasons for measuring the solar UV spectral irradiance and its variations listed in the proposal (pages 5-6) were written by me. I was more interested in photochemical processes than in climate. Remember, 1978 was before the phrase "global warming" was coined; it was even before the ozone "hole" was discovered, the increased interest in ozone around the time period of the proposal coming from concern over the effects of flurocarbons and concern about the effect of a fleet of high-flying SST's in the stratosphere. Besides, the UARS proposal was supposed to be aimed at the Upper Atmosphere, the "UA" in UARS (stratosphere to lower thermosphere), not the troposphere. Also, including the atmospheric reasons was more to demonstrate that members of the SUSIM team were knowlegable in that area than to justify the need for such a solar monitor; the strawman payload listed in the Conceptual Planning Guide for the AO included an instrument (called a "Solar Ultraviolet Spectrometer") whose purpose (given as "Full disk solar irradiance measurements from 120 nm to 400 nm") was justified in the AO itself, in terms of the solar UV irradiance being a major source of "energy input .. in the upper atmosphere". The strawman payload had been defined by a Science Working Group NASA established in October 1977 "to study the need for and the possible implementation of an Upper Atmospheric Research Satellites program". The final report of this working group (JPL Publication 78-54, July 15,1978) listed as number one of the highest priority key scientific questions to be answered by a UARS program: "What is the solar spectrum and its temporal variation between the wavelengths of 120 and 400 nm?"
Q2. Was there intensified interest around the time of the proposal in the question of solar variability? Had the 1976 publication of Jack Eddy's paper on the Maunder Minimum significantly stimulated interest? Was your group influenced by that paper?
A2. There was a bit more interest in the question of solar variability IN THE UV and EUV around the time of the proposal. In my opinion, this was not especially due to Jack Eddy's paper (which did not address directly those portions of the solar spectrum), but, rather to two other publications: the COSPAR Working Group IV report (1976) which compared existing measurements of the solar flux in the EUV and UV, and the book "The Solar Output and Its Variation" (1977), which contained some controversial assessments about the UV variations. Also, around 1978, at scientific meetings, Hans Hinteregger was presenting preliminary time series of measurements of the full-sun Lyman-alpha flux (121.567 nm) from his instrument aboard AE-E satellite, the magnitude of which was much greater than any previously reported measurement of Lyman-alpha (thus raising the question about the solar cycle variation in this emission from atomic hygrogen that plays an important role in aeronomy).
Q3. Did the proposal request funding from NASA, or only space on the UARS? Did the NRL provide the funding for SUSIM? If so, did SUSIM simply represent a continuation of the Navy's long-term interest in upper-atmosphere phenomena, especially as they influence communications? Or were there other motivations for Naval interest in the project? Were there other sources of funding for SUSIM?
A3. The NASA contract in support of SUSIM was the only source of funding for the instrument, its calibration and flight, and the reduction of its data. Other funding from the Navy, for OTHER projects, has paid parts of some salaries. [NRL has not traditionally funded the development of compete solar instruments for satellites ever since these became very expensive because of the quality needed for the hardware to survive years of operation in space. Also, although the Navy IS interested in phenomena that affect communications, relative to the atmosphere that traditionally has meant phenomena that affect the F region of the ionosphere; the part of the solar spectrum SUSIM measures has little effect on the F region (although there are spectral intervals within the pass-band measured by SUSIM which do effect the lower E region and the D region, e.g. near the strong solar Lyman-alpha emission line (121.57 nm), which, by coincidence, occurs at a wavelength where the absorption coefficient of molecular oxygen is small, molecular oxygen and ozone being the two major absorbers of solar UV radiation). The Navy has provided some "seed" money for developing instrumentation that has been tested on sounding-rocket flights and, later, was incorporated into satellite instruments; and it does provide salary support for some solar data-analysts.]