We present the Spectroscopic Time-Resolving Observatory for Broadband Energy X-rays (STROBE-X), a probe-class mission concept selected for study by NASA. It combines huge collecting area, high throughput, broad energy coverage, and excellent spectral and temporal resolution in a single facility. STROBE-X offers an enormous increase in sensitivity for X-ray spectral timing, extending these techniques to extragalactic targets for the first time. It is also an agile mission capable of rapid response to transient events, making it an essential X-ray partner facility in the era of time-domain, multi-wavelength, and multimessenger astronomy. Optimized for study of the most extreme conditions found in the Universe, its key science objectives include: • Robustly measuring mass and spin and mapping inner accretion flows across the black hole mass spectrum, from compact stars to intermediate-mass objects to active galactic nuclei. • Mapping out the full mass-radius relation of neutron stars using an ensemble of nearly two dozen rotation-powered pulsars and accreting neutron stars, and hence measuring the equation of state for ultradense matter over a much wider range of densities than explored by NICER. • Identifying and studying X-ray counterparts (in the post-Swift era) for multiwavelength and multi-messenger transients in the dynamic sky through cross-correlation with gravitational wave interferometers, neutrino observatories, and high-cadence time-domain surveys in other electromagnetic bands. • Continuously surveying the dynamic X-ray sky with a large duty cycle and high time resolution to characterize the behavior of X-ray sources over an unprecedentedly vast range of time scales. STROBE-X's formidable capabilities will also enable a broad portfolio of additional science including accretion physics, stellar evolution, stellar flares, gamma-ray bursts, tidal disruption events, active galactic nuclei, clusters of galaxies, and axion searches. STROBE-X carries three instruments: • The X-ray Concentrator Array (XRCA) covers the soft or low-energy band (0.2-12 keV) with an array of lightweight optics (3 m focal length) that concentrate incident photons onto small solid-state detectors with CCD-level (85-175 eV) energy resolution, 100 ns time resolution, and low background rates. This technology has been fully developed for NICER and will be scaled up to take advantage of the longer focal length of XRCA, which provides an order-of-magnitude improvement in effective area over NICER with over 2.1 m2. • The Large Area Detector (LAD) covers the harder or higher-energy band (2-30 keV or beyond), with modules of Si drift detectors and micropore collimators originally developed for the European LOFT mission concept. LAD provides an order-of-magnitude improvement in both effective area (5.1 m2) and spectral resolution (200-300 eV) over RXTE/PCA. • The Wide-Field Monitor (WFM) will act as a trigger for pointed observations of X-ray transients and will also provide high duty-cycle, high time-resolution, and high spectral-resolution monitoring of the dynamic X-ray sky over the 2-50 keV band. WFM will have 15 times the sensitivity of the RXTE All-Sky Monitor, enabling multi-wavelength and multimessenger investigations with a large instantaneous field of view, down to a new, order-of-magnitude lower flux regime. The STROBE-X mission does not require any new technologies to be developed. The XRCA is a small modification of the flight-proven optics and detectors from NICER, while the LAD and WFM are based on large-area silicon drift detectors already used in experiments at the Large Hadron Collider as well as microchannel plate collimators that have multiple commercial vendors available. In addition, the spacecraft relies only on high-Technology Readiness Level (TRL) components. During our study, we produced detailed instrument and mission designs working with the Integrated Design Center (IDC) at NASA/GSFC. We constructed master equipment lists (MELs) down to the component level for both the instruments and the mission, and we validated our parts acquisition and screening strategy and optimized our design to facilitate manufacture, assembly, integration and test flow. Based on these efforts, we produced a realistic development schedule assuming a Phase A start of October 1, 2023 that yields a launch date of January 1, 2031. The final result of our study is a mission cost estimate. The instrument and spacecraft costs are parametric cost estimates from PRICE-H and SEER, driven by the detailed MELs and using a common set of assumptions for a Class B mission. To that hardware cost, we applied standard percentage multipliers for the other work breakdown structure (WBS) elements and 25% reserves, a $150M fixed charge for launch services giving a total mission lifecycle cost estimate of $880M (FY2018 dollars). This fits within the maximum probe-class budget of $1000M with an additional 13% margin beyond the reserves, giving us high confidence that this mission is executable as a probe. STROBE-X is a highly executable probe-class mission that is ready for construction in the 2020s. This mission is poised to deliver high-impact science in the 2030s that will address some of the highest priority science questions about the formation, evolution, and accretion processes of black holes, the nature of dense matter and gravity, and a wide range of cosmic explosions.
|State||Published - Mar 7 2019|