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Titan Science with the James Webb Space Telescope
The James Webb Space Telescope (JWST), scheduled for launch in 2018, is the successor to the Hubble Space Telescope (HST) but with a signicantly larger aperture (6.5 m) and advanced instrumentation focusing on infrared science (0.6-28.0 microns). In this paper, we examine the potential for scientic investigation of Titan using JWST, primarily with three of the four instruments: NIRSpec, NIRCam, and MIRI, noting that science with NIRISS will be complementary. Five core scientic themes are identied: (1) surface (2) tropospheric clouds (3) tropospheric gases (4) stratospheric composition, and (5) stratospheric hazes. We discuss each theme in depth, including the scientic purpose, capabilities, and limitations of the instrument suite and suggested observing schemes. We pay particular attention to saturation, which is a problem for all three instruments, but may be alleviated for NIRCam through use of selecting small sub-arrays of the detectorssufcient to encompass Titan, but with signicantly faster readout times. We nd that JWST has very signicant potential for advancing Titan science, with a spectral resolution exceeding the Cassini instrument suite at near-infrared wavelengths and a spatial resolution exceeding HST at the same wavelengths. In particular, JWST will be valuable for time-domain monitoring of Titan, given a ve- to ten-year expected lifetime for the observatory, for example, monitoring the seasonal appearance of clouds. JWST observations in the post-Cassini period will complement those of other large facilities such as HST, ALMA, SOFIA, and next-generation ground-based telescopes (TMT, GMT, EELT).
Status of the JWST Science Instrument Payload
The James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM) system consists of five sensors (4 science): Mid-Infrared Instrument (MIRI), Near Infrared Imager and Slitless Spectrograph (NIRISS), Fine Guidance Sensor (FGS), Near InfraRed Camera (NIRCam), Near InfraRed Spectrograph (NIRSpec); and nine instrument support systems: Optical metering structure system, Electrical Harness System; Harness Radiator System, ISIM Electronics Compartment, ISIM Remote Services Unit, Cryogenic Thermal Control System, Command and Data Handling System, Flight Software System, Operations Scripts System.
Stray Light Modeling of the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM)
This paper describes an integrated stray light model of each Science Instrument (SI) in the Integrated Science Instrument Module (ISIM) of the James Webb Space Telescope (JWST) and the Optical Telescope Element Simulator (OSIM), the light source used to characterize the performance of ISIM in cryogenic-vacuum tests at the Goddard Space Flight Center (GSFC). We present three cases where this stray light model was integral to solving questions that arose during the testing campaign - 1) ghosting and coherent diffraction from hardware surfaces in the Near Infrared Imager and Slitless Spectrograph (NIRISS) GR700XD grism mode, 2) ghost spots in the Near Infrared Camera (NIRCam) GRISM modes, and 3) scattering from knife edges of the NIRCam focal plane array masks.
Relative Throughput of the Near-IR Science Instruments for the James Webb Space Telescope as Measured During Ground Testing the Integrated Science Instrument Module
Data were obtained for the purpose of measuring the relative throughput of the Near-IR Science Instruments (SIs) of the James Webb Space Telescope (JWST) as part of the second and third cryogenic-vacuum tests (CV2CV3) of the Integrated Science Instrument Module (ISIM) conducted at the Goddard Space Flight Center (GSFC) in 2014 and 20152016, at the beginning and end of the environmental test program, respectively. This Poster focuses on data obtained as part of the Initial Optical Baseline and as part of the Final Performance test -- two epochs that roughly bracket the CV3 test. The purpose of the test is to trend relative throughput to monitor for any potential changes from gross problems such as contamination or degradation of an optical element. Point source data were taken at a variety of wavelengths for NIRCam Module A and Module B, NIRSpec, NIRISS, Guider 1 and Guider 2 using the Laser Diode (LD) 1.06 micron, LD 1.55 micron, 2.1 micron LED and 3.5 micron LED, as well as for NIRCam Mod A and B and NIRISS using a tungsten source and the F277W, and F480M filters. Spectra were taken using the G140M, G235M, and G395M gratings for NIRSpec, the GRISMR grism for NIRCam Mod A and B and the GR150C grism for NIRISS. The results of these measurements are compared to what would be expected given the efficiency of each of the optical elements in each SI. Although these data were taken as a check against gross problems, they can also be used to provide the first relative throughput estimate for each SI through the various filters source wavelengths measured in their flight-like configurations.