The full mission optic is made from parabolic and hyperbolic silicon mirror pairs, developed by Will Zhang and his team at NASA GSFC, co-aligned onto a supporting shell. The mirror pairs are mounted evenly above and below this shell before the complete structure is mounted onto a spider. This lightweight optic should provide a PSF of < 5 arcseconds HEW.

The camera was designed, built and tested by XCAM Ltd and the CEI at the Open University. It is based around four Teledyne e2v CCD207-40 EM-CCDs: three are spectral and detect the diffracted X-rays, and the central detector samples the optic focus. The central EM-CCD is first used to confirm the telescope pointing in optical light before a filter wheel switches it to X-ray mode. The detectors are cooled to −100 °C with liquid nitrogen to minimize dark current and maximize multiplication gain.

A dedicated readout system, developed with XCAM Ltd and the CEI, uses four BeagleBone Black platforms for readout and digital signal processing. Each spectral EM-CCD is read out every 7.7 seconds; thresholds are applied, X-ray events are identified and telemetered to the ground, and full frames are saved on board. The central detector is read every 0.7 seconds. In optical mode a centroid of the focus is calculated on each frame and used to command the rocket to centre the target; the central 100 × 100 pixel region is telemetered to the ground. In X-ray mode the neutral density filter is swapped for an optical blocking filter so the optic PSF can be measured.

• NASA Goddard: NASA’s new lightweight X-ray mirrors ready for try-outs in space (August 2019)

The spectrometer is built around three main components:

• Passive focusers – each channel has a focuser made of a series of wire grids with progressively finer spacing towards the focal plane, so only X-rays travelling along the intended lines of sight reach the gratings.
• Reflection gratings – the dispersive element; X-rays are diffracted according to wavelength, so where they land on the focal plane encodes their energy. The gratings were fabricated at Penn State.
• Focal plane camera – 11 Teledyne CIS113 CMOS detectors butted into a large-format focal plane.

• Penn State News: Penn State’s high-precision X-ray instrument makes its first trip to space (September 2022)
• Eberly College of Science: the same story on the college site (September 2022)
• NASA: High-precision X-ray instrument will make its first trip to space (September 2022)

The grating alignment method developed at the University of Iowa had some flaws. The main concern was that the grating position depended strongly on the room temperature while the epoxy cured: if the temperature changed, so did the grating position.

To control this, a Praecis ATCU-5 temperature control unit was added, controlling the temperature in the enclosure 50 times better than the room. Further upgrades were planned for the OGRE alignment: replacing the Shack-Hartmann sensor with an interferometer and moving the module motion control to a hexapod. The alignment tolerances for WRX-R were loose enough that the Iowa setup could be used, because WRX-R was a diffuse-source spectrometer for which high resolving power was not possible.

Further steps to improve alignment accuracy and the speed of populating grating modules include:

• Wedged gratings with direct silicon bonding, using the method developed for Silicon Pore Optics at cosine, with the gratings wedged to fan out and match the convergence of the X-ray optic
• Wedged gratings with mechanical constraints, if direct bonding is impracticable
• Precision-machined constraints, using wire EDM to machine bosses that align the gratings
• The XMM-Newton RGS method, with precision-machined surfaces and spring clips constraining the grating surface

The detector is proposed to have 35 stations. Each station has 3 strings carrying dipole antennas embedded up to 100 m in the ice, capturing the horizontal and vertical polarization of the Askaryan signal and working in conjunction with surface antennas. The detector triggers on impulsive radio signals from neutrino-nucleon interactions in the ice. In 2024 I spent five weeks at Summit Station performing experiments to improve our understanding of radio propagation in ice.