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Here's an exceprt from the recent question

The claim may refer to the band labeled U4 in the Celescope Catalog of Ultraviolet Stellar Observations, which refers to a filter with a spectral response centered around 1500 Angstroms and sensitive over a range from about 1200 to 1900 Angstroms. Of the four ultraviolet filters used in that catalog, U4 covered the "most extreme" ultraviolet span.

I thought that "Celescope" might be a typo but checking the link, its title is

Celescope catalog of ultraviolet stellar observations

While the report is about 250 pages long, the first line of the abstract tells us:

The catalog contains the observational results obtained by the Celescope Experiment during the first 16 months of operation of NASA's Orbiting Astronomical Observatory (OAO-2).

and there is even a Wikipedia section Orbiting Astronomical Observatory 2 - Celescope: Smithsonian Astrophysical Observatory which explains that it's an array of four telescopes equipped with UV-sensitive vidicon photocathodes. The article's link to the Uvidicon's page at the Smithsonian Museum has gone dead.

There are two questions about potentially similar UV astronomical telescopes of the same period (early 1970's) in Space Exploration SE:

so possibly the technology of the imaging system itself is similar.

Question(s): But I'd like to ask

  1. How were these four telescopes used? Were they pointed as a cluster, near the same direction as the main telescope, or in four very different directions (eg. every 90°, or tetrahedrally?) Did the observatory spin, where they scanned?

  2. How was the name "Celescope" coined exactly? Who thought it up?

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Unless otherwise indicated all of the information in this answer is from Project Celescope: an Astrophysical Reconnaissance Satellite (PDF).

Question 1: How were these four telescopes used? Were they pointed as a cluster, near the same direction as the main telescope, or in four very different directions (eg. every 90°, or tetrahedrally?) Did the observatory spin, where they scanned?

There were multiple experimental objectives for Celescope:

  1. All-sky Survey
  2. Slitless Spectra
  3. The Solar System
  4. Objects of Special Interest
  5. Calibration Techniques
  6. Stellar Distribution and Speed of Completion of Survey

It appears that the four telescopes, while similar, are not identical, and are aligned with the same axis to cover the same field of view. The first three instruments are imaging systems, each covering a different region of the ultraviolet spectrum and the forth is a slitless spectroscope. The table below summarizes the wavelength bands of each of the imaging systems.

Wavelength Span
Type A 2000 - 3000 Å
Type B 1100 - 2000 Å
Type C 1270 - 1500 Å

The instantaneous field of view of the system is 2.4 degrees. (I assume this is the diameter of a circular field of view.)

Observational centers were spaced by 2.2 degrees to provide overlap in the observational fields of view with a slew of the instrument required between regions.

We are allowed an average of four such slews per orbit. However, transfer between the University of Wisconsin and the Smithsonian experiments and slewing to standard fields for calibration will probably limit us to a working average of three slews per orbit.... Our anticipated time for completion of the program is therefore 400 days.

Question 2: How was the name "Celescope" coined exactly? Who thought it up?

According to Project Celescope: an Astrophysical Reconnaissance Satellite it stands for CELEstial teleSCOPE:

In September of 1958, the Smithsonian Astrophysical Observatory presented to the National Aeronautics and Space Administration a research proposal for these ultraviolet television studies. From this proposal has grown Project Celescope, named for its pioneering use of a truly celestial telescope.

Note: in the original text the letters in bold above were actually underlined.

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    $\begingroup$ This is interesting! During the cold war it was probably important to address what telescopes in low Earth orbit would be looking at for public consumption and for government agencies. These days when we hear "space telescope" we automatically thing of celestial targets, but in 1958... $\endgroup$
    – uhoh
    Mar 26, 2023 at 11:22

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