The Large Observatory For x-ray Timing (LOFT) is a mission concept which was proposed to ESA as M3 and M4 candidate in the framework of the Cosmic Vision 2015-2025 program. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument and the uniquely large field of view of its wide field monitor, LOFT will be able to study the behaviour of matter in extreme conditions such as the strong gravitational field in the innermost regions close to black holes and neutron stars and the supra-nuclear densities in the interiors of neutron stars. The science payload is based on a Large Area Detector (LAD, >8m<sup>2</sup> effective area, 2-30 keV, 240 eV spectral resolution, 1 degree collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g., GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the current technical and programmatic status of the mission.
LOFT (Large Observatory For x-ray Timing) is one of the ESA M3 missions selected within the Cosmic Vision program in 2011 to carry out an assessment phase study and compete for a launch opportunity in 2022-2024. The phase-A studies of all M3 missions were completed at the end of 2013. LOFT is designed to carry on-board two instruments with sensitivity in the 2-50 keV range: a 10 m<sup>2</sup> class Large Area Detector (LAD) with a <1° collimated FoV and a wide field monitor (WFM) making use of coded masks and providing an instantaneous coverage of more than 1/3 of the sky. The prime goal of the WFM will be to detect transient sources to be observed by the LAD. However, thanks to its unique combination of a wide field of view (FoV) and energy resolution (better than 500 eV), the WFM will be also an excellent monitoring instrument to study the long term variability of many classes of X-ray sources. The WFM consists of 10 independent and identical coded mask cameras arranged in 5 pairs to provide the desired sky coverage. We provide here an overview of the instrument design, configuration, and capabilities of the LOFT WFM. The compact and modular design of the WFM could easily make the instrument concept adaptable for other missions.
The Large Observatory For x-ray Timing (LOFT) was studied within ESA M3 Cosmic Vision framework and participated in the final downselection for a launch slot in 2022-2024. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument, LOFT will study the behaviour of matter under extreme conditions, such as the strong gravitational field in the innermost regions of accretion flows close to black holes and neutron stars, and the supranuclear densities in the interior of neutron stars. The science payload is based on a Large Area Detector (LAD, 10 m<sup>2 </sup> effective area, 2-30 keV, 240 eV spectral resolution, 1° collimated field of view) and a Wide Field Monitor (WFM, 2-50 keV, 4 steradian field of view, 1 arcmin source location accuracy, 300 eV spectral resolution). The WFM is equipped with an on-board system for bright events (e.g. GRB) localization. The trigger time and position of these events are broadcast to the ground within 30 s from discovery. In this paper we present the status of the mission at the end of its Phase A study.
The Large Observatory For X-ray Timing (LOFT) is one of the 5 missions considered by ESA as an M3 candidate. The LOFT scientific payload consists of a collimated Large Area Detector (LAD) and a Wide Field Monitor (WFM).
The scale of the LAD (10 m² effective area) puts it in a new design space for X-ray astronomy, with resulting implications for design trade-offs, modularity, manufacturing, assembly, test and calibration processes. This paper focuses on the LAD module, which is the building block of the instrument. We present the overall module design, discussing these challenges and how they have been addressed.
The space mission LOFT (Large Observatory For X-ray Timing) was selected in 2011 by ESA as one of the candidates for the M3 launch opportunity. LOFT is equipped with two instruments, the Large Area Detector (LAD) and the Wide Field Monitor (WFM), based on Silicon Drift Detectors (SDDs). In orbit, they would be exposed to hyper-velocity impacts by environmental dust particles, which might alter the surface properties of the SDDs. In order to assess the risk posed by these events, we performed simulations in ESABASE2 and laboratory tests. Tests on SDD prototypes aimed at verifying to what extent the structural damages produced by impacts affect the SDD functionality have been performed at the Van de Graaff dust accelerator at the Max Planck Institute for Nuclear Physics (MPIK) in Heidelberg. For the WFM, where we expect a rate of risky impacts notably higher than for the LAD, we designed, simulated and successfully tested at the plasma accelerator at the Technical University in Munich (TUM) a double-wall shielding configuration based on thin foils of Kapton and Polypropylene. In this paper we summarize all the assessment, focussing on the experimental test campaign at TUM.
LOFT (Large Observatory for X-ray Timing) is one of the five candidates that were considered by ESA as an M3 mission (with launch in 2022-2024) and has been studied during an extensive assessment phase. It is specifically designed to perform fast X-ray timing and probe the status of the matter near black holes and neutron stars. Its pointed instrument is the Large Area Detector (LAD), a 10 m<sup>2</sup>-class instrument operating in the 2-30keV range, which holds the capability to revolutionise studies of variability from X-ray sources on the millisecond time scales. <p> </p>The LAD instrument has now completed the assessment phase but was not down-selected for launch. However, during the assessment, most of the trade-offs have been closed leading to a robust and well documented design that will be reproposed in future ESA calls. In this talk, we will summarize the characteristics of the LAD design and give an overview of the expectations for the instrument capabilities.
The Large Observatory for X-ray Timing (LOFT) is one of the five mission candidates that were considered by ESA for an M3 mission (with a launch opportunity in 2022 - 2024). LOFT features two instruments: the Large Area Detector (LAD) and the Wide Field Monitor (WFM). The LAD is a 10 m<sup>2</sup>-class instrument with approximately 15 times the collecting area of the largest timing mission so far (RXTE) for the first time combined with CCD-class spectral resolution. The WFM will continuously monitor the sky and recognise changes in source states, detect transient and bursting phenomena and will allow the mission to respond to this. Observing the brightest X-ray sources with the effective area of the LAD leads to enormous data rates that need to be processed on several levels, filtered and compressed in real-time already on board. The WFM data processing on the other hand puts rather low constraints on the data rate but requires algorithms to find the photon interaction location on the detector and then to deconvolve the detector image in order to obtain the sky coordinates of observed transient sources. In the following, we want to give an overview of the data handling concepts that were developed during the study phase.
The LOFT mission concept is one of four candidates selected by ESA for the M3 launch opportunity as Medium Size missions of the Cosmic Vision programme. The launch window is currently planned for between 2022 and 2024. LOFT is designed to exploit the diagnostics of rapid X-ray flux and spectral variability that directly probe the motion of matter down to distances very close to black holes and neutron stars, as well as the physical state of ultradense matter. These primary science goals will be addressed by a payload composed of a Large Area Detector (LAD) and a Wide Field Monitor (WFM). The LAD is a collimated (<1 degree field of view) experiment operating in the energy range 2-50 keV, with a 10 m<sup>2</sup> peak effective area and an energy resolution of 260 eV at 6 keV. The WFM will operate in the same energy range as the LAD, enabling simultaneous monitoring of a few-steradian wide field of view, with an angular resolution of <5 arcmin. The LAD and WFM experiments will allow us to investigate variability from submillisecond QPO’s to yearlong transient outbursts. In this paper we report the current status of the project.
The Large Observatory For X-ray Timing (LOFT), selectyed by ESA as one of the four Cosmic Visiion M3 candidate missions to undergo an assessment phase, will revolutionize the study of compact objects in our galaxy and of the brightest supermassive black holes in active galactic nuclei. The Large Area Detector (LAD), carrying an unprecedented effective area of 10 m2, is complemented by a coded-mask Wide Field Monitor, in charge of monitoring a large fraction of the sky potentially accesesible to the LAD, to provide the history and context for the sources observed by LAD and to trigger its observations on their most interesting and extreme states. In this paper we present detailed simulations of the imaging capabilities of the Silicon Drift Detectors developed for the LOFT Wide Field Monitor detection plane. The simulations explore a large parameter space for both the detector design and the environmental conditions, allowing us to optimize the detector characteristcs and demonstrating the X-ray imaging performance of the large-area SDDs in the 2-50 keV energy band.
LOFT (Large Observatory For x-ray Timing) is one of the four missions selected in 2011 for assessment study for the
ESA M3 mission in the Cosmic Vision program, expected to be launched in 2024. The LOFT mission will carry two
instruments with their prime sensitivity in the 2-30 keV range: a 10 m<sup>2 </sup>class large area detector (LAD) with a <1°
collimated field of view and a wide field monitor (WFM) instrument based on the coded mask principle, providing
coverage of more than 1/3 of the sky. The LAD will provide an effective area ~20 times larger than any previous mission
and will by timing studies be able to address fundamental questions about strong gravity in the vicinity of black holes
and the equation of state of nuclear matter in neutron stars. The prime goal of the WFM will be to detect transient
sources to be observed by the LAD. However, with its wide field of view and good energy resolution of <300 eV, the
WFM will be an excellent monitoring instrument to study long term variability of many classes of X-ray sources. The
sensitivity of the WFM will be 2.1 mCrab in a one day observation, and 270 mCrab in 3s in observations of in the
crowded field of the Galactic Center. The high duty cycle of the instrument will make it an ideal detector of fast transient
phenomena, like X-ray bursters, soft gamma repeaters, terrestrial gamma flashes, and not least provide unique
capabilities in the study of gamma ray bursts. A dedicated burst alert system will enable the distribution to the
community of ~100 gamma ray burst positions per year with a ~1 arcmin location accuracy within 30 s of the burst. This
paper provides an overview of the design, configuration, and capabilities of the LOFT WFM instrument.
The Large Observatory for X-ray Timing (LOFT) is one of the four candidate ESA M3 missions considered for launch in
the 2022 timeframe. It is specifically designed to perform fast X-ray timing and probe the status of the matter near black
holes and neutron stars. The LOFT scientific payload is composed of a Large Area Detector (LAD) and a Wide Field
Monitor (WFM). The LAD is a 10 m<sup>2</sup>-class pointed instrument with 20 times the collecting area of the best past timing
missions (such as RXTE) over the 2-30 keV range, which holds the capability to revolutionize studies of X-ray
variability down to the millisecond time scales. Its ground-breaking characteristic is a low mass per unit surface,
enabling an effective area of ~10 m<sup>2</sup> (@10 keV) at a reasonable weight. The development of such large but light
experiment, with low mass and power per unit area, is now made possible by the recent advancements in the field of
large-area silicon detectors - able to time tag an X-ray photon with an accuracy <10 μs and an energy resolution of ~260
eV at 6 keV - and capillary-plate X-ray collimators. In this paper, we will summarize the characteristics of the LAD
instrument and give an overview of its capabilities.
The Large Observatory for X-ray Timing (LOFT) is one of the four candidate ESA M3 missions considered for
launch in the timeframe of 2022. It is specifically designed to perform fast X-ray timing and probe the status of
the matter near black holes and neutron stars. The LOFT scientific payload consists of a Large Area Detector
and a Wide Field Monitor.
The LAD is a 10m<sup>2</sup>-class pointed instrument with high spectral (200 eV @ 6 keV) and timing (< 10 μs)
resolution over the 2-80 keV range. It is designed to observe persistent and transient X-ray sources with a very
large dynamic range from a few mCrab up to an intensity of 15 Crab.
An unprecedented large throughput (~280.000 cts/s from the Crab) is achieved with a segmented detector,
making pile-up and dead-time, often worrying or limiting focused experiments, secondary issues.
We present the on-board data handling concept that follows the highly segmented and hierarchical structure
of the instrument from the front-end electronics to the on-board software. The system features customizable
observation modes ranging from event-by-event data for sources below 0.5 Crab to individually adjustable time
resolved spectra for the brighter sources. On-board lossless data compression will be applied before transmitting
the data to ground.
The High Energy X-ray Imager Survey <i>(HEXIS)</i> Coded Mask balloon instrument will test the performance of
the electronics and the detector for the proposed MIRAX satellite mission, and measure the background in a
near space environment. HEXIS is a Coded Mask Imager based upon a 100 x 100mm Tungsten MURA mask
and a set of four Cadmium-Zinc-Telluride (CZT) crossed strip detectors assembled as one detector module with
40 cm<sup>2</sup> detector area and 0.5mm pitch strips creating an effective 126 x 126 grid of 0.5 x 0.5mm<sup>2</sup> pixels. Each
detector strip can be read out individually using Readout Electronics for Nuclear Application (RENA)-ASICs
developed by NOVA R&D. The system has an operating energy range of <10 to 200 keV. The telescope has a
passive shield as part of the instrument structure, which is surrounded by an active anti-coincidence shield of
plastic scintillators with embedded wavelength shifting and light transmitting fibers. The first HEXIS balloon
flight is planned for Spring 2007. We present the lab performance for one module using RENA ASICs and for
the scintillator shield. The MIRAX Hard X-ray Imager (HXI) will contain two cameras with 9 detector modules
We present the Event Pre Processor (EPP) for the Cadmium-Zinc-Telluride-strip detector of the Hard X-ray Imager (HXI) onboard of the <i>MIRAX</i> satellite. The purpose of the EPP is to provide an onboard data reduction and event filtering by applying a non linear energy gain correction for each detector strip. This data reduction is necessary because of the limited telemetry capacity of the <i>MIRAX</i> satellite. We decided to use hardwired data processing electronics based on a Field Programmable Gate Array (FPGA) chip designed in VHDL. This solution allows us to combine high computation power with low power consumption. We discuss the functionality and status of the EPP design developed in T&diaeru;bingen.