Feldman: If I read the proposal correctly, you are requesting support for development of the calorimeter -- rather than, for example, support for its deployment in a particular series of measurements or aboard any particular platform.
Hoyt: This is correct.
Feldman: To what agency was the proposal made?
Hoyt: To NASA.
Feldman: Was it funded?
Hoyt: No. It finsihed number 2 or 3 (behind Willson's ACRIM proposal) out of 50 submitted.
Feldman: How successful was the particular instrument described here?
Hoyt: It wasn't built, but Dale West who built similar radiometers was confident that a 0.1% absolute accuracy could be acheived.
Feldman: Can you briefly describe the principles of the instrument's operation?
Hoyt: There are two classes of radiometers 1) power meters like ACRIM, PACRAD, and the Angstrom pyrheliometer for example, and 2) energy meters like the calorimeter described or the silver disk pyrheliometer. The energy meters attempt to capture and store the incoming energy, allowing little of to escape. The instrument can be calibrated by inputting a well measured amount of electrical energy and tracking the temperature changes of the cavity. When an unknown amount of light impinges on the radiometer for a fixed interval, the changes in temperature can be used to calculate the light's total irradiance.
Feldman: In what ways did it represent significant improvement over earlier instruments?
Hoyt: If developed, I believe it would have been more accurate than other instruments, so joining time series of solar irradiance by different instruments would have been better. a break in the time series (no instrument flying) would have less serious consequences for climate and solar studies.
Feldman: Where does this proposal fit among various other attempts to measure total solar irradiance?
Hoyt: There were earlier proposals to measure the solar irradiance, but none were funded until Willson's ACRIM and the Hickey-Frieden radiometer on Nimbus-7.
Feldman: Weaknesses of the proposed instrument?
Hoyt: I still think the instrument is better than the ones being flown today. Perhaps the major weakness of the instrument is its size. A large size is helpful in making accurate measurements, but most platforms would prefer smaller instruments.