The James Webb Space Telescope: Mission overview and status

Abstract

Abstract- l. DESIGNING FOR DISCOVERYThe science motivation for the JWST mission was developed by a succession of international science working groups and is described by Gardner et aI. 2006, with updates maintained by the lWST flight science working group 1 at: http://www.stsci.eduljwst/sciencelwhitepapersi . This science case fonns the basis from which detailed science and mission requirements were derived to guide engineering design and development of the lWST as a research tool. The science observations that are actually implemented by the lWST will be proposed by the international astronomical community in response to annual peer reviewed proposal opportunities. The discovery potential of the lWST relative to other concurrent facilities is discussed in Thronson, Stiavelli, and Tielens 2009.The emergence of the first sources of light in the universe (after decoupling) marks the end of the "Dark Ages" in cosmic history (Rees 1997). The ultraviolet radiation field produced by these sources created the ionization that is observed in the local intergalactic medium (10M). The JWST design provides Unique capability to address key questions about this era in cosmic The lWST architecture is prinuirily shaped by requirements associated with answering the above questions. In contrast to the Hubble Space Telescope (HST), the lWST is designed as an infrared optimized telescope to observe the redshifted ultraviolet radiation from the first galaxies and supernovae of the flfSt stars. To achieve the nly sensitivity needed to observe this era (z -6-20), the observatory must have a telescope aperture that is larger in diameter than the largest rocket faring, and the entire optical system must be cooled to -40-50 K. Finally, the resulting large deployable cryogenic telescope must achieve HST-like angular resolution across the SWIR spectrum. The major observatory design features trace directly from these requirements and differ markedly from those of the HST.The lWST science instrument payload is designed to probe the first galaxies with high angular resolution nearinfrared image surveys in broad-band filters. This capability enables identification of primeval galaxies by searching their Lyman continuum break with multi-filter photometry. This prominent feature occurs in the near-infrared (1.3 -2.6 um) for galaxies with redshifts in the range of 10 -20. This broad-band technique exploits the maximum sensitivity of the observatory, such that the space density of galaxies can be probed to z-20. lWST high angular resolution imagery across the 0.6 -29 um spectrum will probe the assembly and evolution of galaxy motphologies to enable observation of when and how the Hubble sequence formed.Tbe lWST is designed to enable near-infrared multiobject spectroscopy of thousands of galaxies at several spectral resolutions (_ 10' , _10'). This capability will probe the chemical evolution and metallicity of galaxies, and the ionization state of the IGM across cosmic time. Low resolution multi-object spectroscopy will enable calibration of ph...

Status of the James Webb Space Telescope integrated science instrument module system

“…Figure 16 shows the ISIM Command and Data Handling (IC&DH) and Remote Services Unit (IRSU) in context of the overall ISIM electrical system. The IC&DH/IRSU hardware and software together provide four major functions: [1] Coordinate collection of science image data from the NIRCam, NIRSpec MIRI, and FGS instruments in support of science objectives; [2] Perform multi-accum & lossless compression algorithms on science image data to achieve data volume reduction needs for on-board storage and subsequent transmission to the ground; [3] Communicate with the Spacecraft Command and Telemetry Processor (CTP) to transfer data to the Solid State Recorder (SSR) and prepare for subsequent science operations; and [4] Provide electrical interfaces to the Thermal Control Sub-system.…”

“…The tasks are contained in an operating system environment that is adapted to the mission-specific hardware components with a set of custom device drivers shown in Figure 21 as OS Services. The tasks can be classified into three categories: (1) Command and Telemetry Services, (2) Applications that operate the Science Instruments (SIs) and support science operations, and (3) System Support Services that manage the task environment and external system interfaces.…”

“…The James Webb Space Telescope (Figure 1) is under development by NASA for launch during 2014 with major contributions from the European and Canadian Space Agencies. The JWST mission is designed to enable a wide range of science investigations across four broad themes: [1] observation of the first luminous objects after the Big Bang, [2] the evolution of galaxies, [3] the birth of stars and planetary systems, and [4] the formation of planets and the origins of life. 1,2,3 Its Integrated Science Instrument Module (ISIM) is the science payload of the JWST.…”

“…The JWST mission is designed to enable a wide range of science investigations across four broad themes: [1] observation of the first luminous objects after the Big Bang, [2] the evolution of galaxies, [3] the birth of stars and planetary systems, and [4] the formation of planets and the origins of life. 1,2,3 Its Integrated Science Instrument Module (ISIM) is the science payload of the JWST. 4,5,6 Along with the telescope and spacecraft, the ISIM is one of three elements that comprise the JWST space vehicle.…”

“…In order to maximize efficiency with respect to mass, power, and nonrecurring engineering cost, the four JWST science instruments are not designed as traditional stand-alone systems; rather, the ISIM provides nine key subsystems that are shared by each of the science instruments. These are the: [1] optical metering structure, [2] ISIM Electronics Compartment (IEC), [3] harness radiator, [4] ISIM Command and Data Handling System (ICDH), [5] ISIM Remote Services Unit (IRSU), [6] electrical harness system, [7] thermal control system, [8] flight software system, and [9] on-board script system. In the following sections, we briefly describe the science instruments (which are covered in detail elsewhere in this conference) and provide detail on their shared support systems.…”