We describe the two 140-mm-aperture simulated blackbody sources used for the on-board calibration of the Along Track Scanning Radiometer, a spaceborne thermal infrared instrument for the accurate remote sensing of sea surface temperature, in operation since 1991. The design of these spaceborne sources, which operate at ≈ -10 °C and ≈ +30 °C, allows them to meet their unprecedented accuracy goal, namely a 3σ uncertainty in their brightness temperature of <0.1 K for the whole mission. This performance is empirically demonstrated in the laboratory and in flight by long-term temperature readout tests, temperature uniformity measurements, and direct emissivity measurements.

We describe an application of the Penning Gas Imager or PGI' in X-ray astronomy. The PGI is an imaging proportional counter with improved energy and position resolution. A space version of the laboratory prototype detector has been designed and built at MSSL for use as a focal plane detector for the Soft X-ray Telescope (SXT). We present an application of the PGI to the imaging of diffraction patterns from biological specimens. Possible use of the PGI on XMM is also briefly discussed.

A Wolter Type I x-ray telescope, intended both for astronomical observations and to serve as a prototype module for the large area modular array of reflectors (LAMAR) mission, is now in definition study under NASA's Spacelab program. The five mirror telescope presently being designed is to have a blur circle radius of 20 arc sec and an effective area of about 400 cm2 at 1/4 keV, 200 cm2 in the 0.5 to 2 keV range, and 50 cm2 between 2 and 5 keV. Future expansion to a full ten mirror telescope will approximately double these effective areas. A rotary interchange mechanism will allow either of two imaging proportional counters (IPCs) to be placed at the telescope focus; one operating between 0.15 and 2 keV and the other optimized for the 0.6 to 6 keV energy range. During flight, the telescope will utilize an instrument pointing system for a series of observations lasting from six minutes to several hours. This investigation has dual objectives: The primary objective is scientific and involves observational study of galactic and extragalactic x-ray sources, extending the work of the Einstein Observatory to much fainter sources and to higher energies. The second objective is to provide an assessment of the cost and improved performance of utilizing Wolter Type l x-ray optics for the LAMAR mission and to extend the technology for producing these optics to still higher angular resolution and toward lower cost.

The 1.4–22.4 Å range of the soft X-ray spectrum includes a multitude of emission lines which are important for the diagnosis of plasmas in the 1.5–50 million degree temperature range. In particular, the hydrogen and helium-like ions of all abundant solar elements with Z > 7 have their primary transitions in this region and these are especially useful for solar flare and active region studies. The soft X-ray polychromator (XRP) is a high resolution experiment working in this spectral region. The XRP consists of two instruments with a common control, data handling and power system. The bent crystal spectrometer is designed for high time resolution studies in lines of Fe i-Fe xxvi and Ca xix. The flat crystal scanning spectrometer provides for 7 channel polychromatic mapping of flares and active regions in the resonance lines of O viii, Ne ix, Mg xi, Si xiii, S xv, Ca xix, and Fe xxv with 14″ spatial resolution. In its spectral scanning mode it covers essentially the entire 1.4–22.5 Å region.

Three ionospheric probes were carried on the ESRO-4 satellite, a spherical gridded probe with swept potential collecting positive ions, a Langmuir probe measuring electron temperature and vehicle potential, and a fixed potential gridded probe measuring fluctuations in total ion density. ESRO-4 was placed in a polar orbit of apogee 1177 km, perigee 245 km on 22 November 1972 and ionospheric data of excellent quality were obtained until the spacecraft's re-entry on 15 April 1974. The instrumentation is described and early results are presented.

The design and construction is described of a package of X-ray telescopes launched in the NASA satellite Copernicus (OAO-3), which began stellar observations in September 1972. It contains three grazing incidence reflectors covering a range of wavelengths from 0.3 to 8 nm, and having a combined collecting area of 40.9 sq cm, with angular resolutions up to 1 minute of arc. This is believed to be the first satellite application of such reflectors in stellar X-ray astronomy. A collimated detector of wavelengths 0.1-0.3 nm has a 17.8 sq cm collecting area. A visible light star tracker detects package misalignment if this should occur.

A theoretical method is given for calculating the amount of support required for pressurized membranes of large breadth-to-thickness ratios. This theory has use in the design of windows for soft X-ray proportional counters.

A system is described which has been built to control the density of the gas in a soft X-ray proportional counter to within +or-0.5% of the desired value when making astrophysical observations from a sounding rocket.