Vigorous technology development is essential for the Beyond Einstein program to succeed. For the Einstein Great Observatories, technology roadmaps are in place; the Beyond Einstein program includes the resources needed to implement them.

Constellation-X will provide X-ray spectral imaging of unprecedented sensitivity to determine the fate of matter as it falls into black holes, and will map hot gas and dark matter to determine how the Universe evolved large-scale structures.

Lightweight, grazing incidence X-ray optics. Each of the four identical Constellation-X spacecraft will carry two sets of telescopes: (1) a spectroscopy X-ray telescope (SXT) for the low energy band up to 10 keV, and (2) three hard X-ray telescopes (HXTs) for the high energy band. Both incorporate highly nested, grazing-incidence X-ray mirror arrays, which must simultaneously meet tight angular resolution, effective area, and mass constraints. Engineering test units of both SXT and HXT mirrors are under development: glass substrates with surfaces replicated from precision mandrels for SXT and HXT, and an alternative replicated nickel shell design for HXT.

X-ray calorimeter arrays. Two technologies are being developed in parallel: semiconducting bolometers and voltage-biased transition-edge superconducting thermistors. Both have made substantial progress toward the required energy resolution of 2 eV. Multiple approaches to fabrication of high-quality arrays and multiplexed readout amplifiers are under development.

Long-lived 50mK coolers. Constellation-X requires reliable long-life first stage coolers operating at 5-10 K. The Advanced Cryocooler Technology Development Program (ACTDP) is already pursuing this goal through study-phase contracts, leading to completion of two demonstration coolers in 2005. The ultimate detector temperature of 50 mK will be reached by one of several adiabatic demagnetization refrigerator technologies currently under study.

Grazing incidence reflection gratings. Reflection gratings dispersed onto CCDs provide imaging spectroscopy in the 0.2-1.5 keV energy range and are similar to those flown on XMM-Newton. For Constellation-X, improvements to reduce weight and increase resolution are under study. Novel event-driven CCDs have recently been developed that provide significant improvements in performance and robustness.

Solid-state hard X-ray imaging detectors. At hard X-ray energies, CdZnTe detectors provide < 1.2 keV resolution and high quantum efficiency over the 6-50 keV energy range. Key requirements have been demonstrated but work is continuing on extending the response at low energies and reducing the effects of electron trapping.

LISA will open a new window on the Universe by enabling the detection of gravitational radiation from a wide variety of astronomical systems. It consists of a triangle of reference masses in solar orbit connected by a precision metrology system. The measurement of the relative motion of these drag-free masses allows us to sense the passage of gravitational waves through the Solar System. To use the capture of compact objects to map spacetime outside of supermassive black holes sets the sensitivity requirements at wave frequencies of 10^-2 to 10^-3 Hz. To measure the properties of merging pairs of supermassive black holes requires good sensitivity down at least to 10^-4 Hz.

The key technologies are those to (1) minimize external disturbances of the reference masses, and (2) precisely measure their separation.

Disturbance Reduction System. Micronewton thrusters keep the spacecraft precisely centered about the masses. Several types which meet LISA's noise requirements have been demonstrated, and lifetime and space testing are planned. Correction signals are sent to the thrusters by gravitational reference units (GRUs), which also serve as the reference mirrors for the laser measurement system. Improvements in existing GRUs (such as those flying on the NASA/German GRACE mission) that will extend LISA's sensitivity below 10^-3 Hz are under development.

Laser Measurement System. LISA's sensitivity above 10^-3 Hz is set by the laser power and the measurement system. Changes in the 5 x 10⁶ km test mass spacing must be measured to 10^-12 m, or 10^-5 fringes. That requirement can be met by existing lasers and detection systems. But orbital dynamics lead to changes in spacecraft spacing that can create a fringe rate as large as 15 MHz. This imposes stringent requirements on laser frequency stability, telescope pointing and dimensional stability, and the phase measurement system, including ultra-stable oscillators.

System Verification. A validation flight is planned in June 2006 on the ESA SMART-2 spacecraft, with US participation through the New Millennium mission ST-7. This program will be an important validation of the critical disturbance reduction system components, the gravitational reference units, micronewton thrusters, and the laser interferometer to measure test mass spacing.