J. W. Miles

Early science with SOFIA, the stratospheric observatory for infrared astronomy

The Stratospheric Observatory For Infrared Astronomy (SOFIA) is an airborne observatory consisting of a specially modified Boeing 747SP with a 2.7 m telescope, flying at altitudes as high as 13.7 km (45,000 ft). Designed to observe at wavelengths from 0.3 μm to 1.6 mm, SOFIA operates above 99.8% of the water vapor that obscures much of the infrared and submillimeter. SOFIA has seven science instruments under development, including an occultation photometer, near-, mid-, and far-infrared cameras, infrared spectrometers, and heterodyne receivers. SOFIA, a joint project between NASA and the German Aerospace Center Deutsches Zentrum fur Luft und-Raumfahrt, began initial science flights in 2010 December, and has conducted 30 science flights in the subsequent year. During this early science period three instruments have flown: the mid-infrared camera FORCAST, the heterodyne spectrometer GREAT, and the occultation photometer HIPO. This Letter provides an overview of the observatory and its early performance.

HIGH-RESOLUTION MID-INFRARED OBSERVATIONS OF NGC 7469

We present a high-resolution 11.7 micrometer image of the starburst/Seyfert hybrid galaxy NGC 7469 using the Hale 5 m telescope at Palomar Observatory. Our map, with diffraction limited spatial resolution of 0.6 sec, shows a 3 sec diameter ring of emission around an unresolved nucleus. The map is similar to the Very Large Array (VLA) 6 cm map of this galaxy made with 0.4 sec resolution by Wilson et al. (1991). About half of the mid-infrared flux in our map emerges from the unresolved nucleus. We also present spatially resolved low resolution spectra that show that the 11.3 micrometer polycyclic aromatic hydrocarbon (PAH) feature comes from the circumnuclear ring but not from the nucleus of the galaxy.

Palomar observations of the R impact of comet Shoemaker-Levy 9: II. Spectra

We present mid-infrared spectroscopic observations from Palomar observatory of the impact of fragment R of comet P/Shoemaker-Levy 9 with Jupiter on 21 July 1994. Low-resolution 8–13 µm spectra taken near the peak of the lightcurve show a broad emission feature that resembles the silicate feature commonly seen in comets and the interstellar medium. We use this feature to estimate the dust content of the impact plume. The overall infrared spectral energy distribution at the time of peak brightness is consistent with emission from an optically-thin layer of small particles at ∼600 K. Integrating over the spectrum and the lightcurve, we obtain a total radiated energy from the R impact of ≥ 2 × 10^(25) ergs and a plume mass of ≥ 3 × 10^(13) g.

Thermal infrared imaging of subarcsecond structure in the trapezium nebula

We present 11.7 and 8.8 micron images of the central region of the Ney-Allen Nebula In Orion which reveal mid-infrared counterparts to the ionized globules previously discovered by optical and radio observations. The 0.5 arcsec full width at half maximum (FWHM) resolution images also reveal several arc-shaped structures which are associated with the compact sources. Each of the arcs points toward theta(sup 1) Ori C, providing further evidence for the strong-effects of the intense radiation and wind from this star on the central Orion Nebula. Low-resolution spectra of a few of these condensations and arcs are similar to spectra of the diffuse, optically thin silicate dust observed throughout the region. Photometry of one of the condensations, however, indicates that is cooler than the others. Simple momentum-balance arguments indicate that dust in the arcs could originate in the outflow from the compact sources and flow outward until stopped by the stellar wind and radiation pressure from theta(sup 1) Ori C.

Palomar observations of the R impact of comet Shoemaker‐Levy 9: I. Light curves

We present near-infrared observations from Palomar observatory of the impact of fragment R of comet Shoemaker-Levy 9 with Jupiter on 21 July 1994. Two instruments were used to image the event at 3.2 and 4.5 microns simultaneously. The lightcurves from these image sequences both show two faint precursor flashes, a bright main peak, and several oscillations over the following hour. We identify the precursor flashes with the entry of the bolide into Jupiters upper atmosphere, and with the post-impact ejecta plume rising above the planets limb. The main peak is due to the re-entry of the collapsing plume into Jupiters atmosphere and the resultant shock heating.

Another neon nova - Early infrared photometry and spectroscopy of Nova Cygni 1992

Infrared photometry and spectrophotometry of Nova Cygni 1992 taken within 54 days of its eruption show a strong 12.8-micron Ne II forbidden emission line as well as hydrogen recombination lines. Spectra with lambda/Delta lambda of about 2000 resolve the Ne II forbidden and 12.37-micron Hu-alpha lines with about 2200 km/s (FWHM). The Ne II forbidden line shows multiple velocity components. The amount of forbidden Ne II required to produce the observed emission feature exceeds the solar abundance of neon by at least a factor of 4.

The high-excitation region of NGC 7027

First detections of the [Na IV] 9.04 μm and the [Ar V] 13.09 μm fine-structure emission lines, observed in the well-studied planetary nebula NGC 7027, are reported. The Na IV 9.04 μm/3242 A line ratio is shown to be an excellent temperature diagnostic for highly ionized regions. With the addition of the Ne V 24.32 μm/3426 A line ratio, an electron temperature of 22400 K and an electron density of log n e = 4.62 are obtained for the inner He +2 region of NGC 7027

Capabilities, performance, and status of the SOFIA science instrument suite

The Stratospheric Observatory for Infrared Astronomy (SOFIA) is an airborne observatory, carrying a 2.5 m telescope onboard a heavily modified Boeing 747SP aircraft. SOFIA is optimized for operation at infrared wavelengths, much of which is obscured for ground-based observatories by atmospheric water vapor. The SOFIA science instrument complement consists of seven instruments: FORCAST (Faint Object InfraRed CAmera for the SOFIA Telescope), GREAT (German Receiver for Astronomy at Terahertz Frequencies), HIPO (High-speed Imaging Photometer for Occultations), FLITECAM (First Light Infrared Test Experiment CAMera), FIFI-LS (Far-Infrared Field-Imaging Line Spectrometer), EXES (Echelon-Cross-Echelle Spectrograph), and HAWC (High-resolution Airborne Wideband Camera). FORCAST is a 5–40 μm imager with grism spectroscopy, developed at Cornell University. GREAT is a heterodyne spectrometer providing high-resolution spectroscopy in several bands from 60–240 μm, developed at the Max Planck Institute for Radio Astronomy. HIPO is a 0.3–1.1 μm imager, developed at Lowell Observatory. FLITECAM is a 1–5 μm wide-field imager with grism spectroscopy, developed at UCLA. FIFI-LS is a 42–210 μm integral field imaging grating spectrometer, developed at the University of Stuttgart. EXES is a 5–28 μm high-resolution spectrograph, developed at UC Davis and NASA ARC. HAWC is a 50–240 μm imager, developed at the University of Chicago, and undergoing an upgrade at JPL to add polarimetry capability and substantially larger GSFC detectors. We describe the capabilities, performance, and status of each instrument, highlighting science results obtained using FORCAST, GREAT, and HIPO during SOFIA Early Science observations conducted in 2011.

Illuminating dark energy with the Joint Efficient Dark-energy Investigation (JEDI)

The Universe appears to be expanding at an accelerating rate, driven by a mechanism called Dark Energy. The nature of Dark Energy is largely unknown and needs to be derived from observation of its effects. JEDI (Joint Efficient Dark-energy Investigation) is a candidate implementation of the NASA-DOE Joint Dark Energy Mission (JDEM). It will probe the effects of Dark Energy in three independent ways: (1) using Type Ia supernovae as cosmological standard candles over a range of distances, (2) using baryon acoustic oscillations as a cosmological standard ruler over a range of cosmic epochs, and (3) mapping the weak gravitational lensing distortion by foreground galaxies of the images of background galaxies at different distances. JEDI provides crucial systematic error checks by simultaneously applying these three independent observational methods to derive the Dark Energy parameters. The concordance of the results from these methods will not only provide an unprecedented understanding of Dark Energy, but also indicate the reliability of such an understanding. JEDI will unravel the nature of Dark Energy by obtaining observations only possible from a vantage point in space, coupled with a unique instrument design and observational strategy. Using a 2 meter-class space telescope with simultaneous wide-field imaging (~ 1 deg2, 0.8 to 4.2 μm in five bands) and multi-slit spectroscopy (minimum wavelength coverage 1 to 2 μm), JEDI will efficiently execute the surveys needed to solve the mystery of Dark Energy.

Execution of the Spitzer in-orbit checkout and science verification plan

The Spitzer Space Telescope is an 85-cm telescope with three cryogenically cooled instruments. Following launch, the observatory was initialized and commissioned for science operations during the in-orbit checkout (IOC) and science verification (SV) phases, carried out over a total of 98.3 days. The execution of the IOC/SV mission plan progressively established Spitzer capabilities taking into consideration thermal, cryogenic, optical, pointing, communications, and operational designs and constraints. The plan was carried out with high efficiency, making effective use of cryogen-limited flight time. One key component to the success of the plan was the pre-launch allocation of schedule reserve in the timeline of IOC/SV activities, and how it was used in flight both to cover activity redesign and growth due to continually improving spacecraft and instrument knowledge, and to recover from anomalies. This paper describes the adaptive system design and evolution, implementation, and lessons learned from IOC/SV operations.