IPAC is responsible for hosting the NASA Herschel Science Center and the US Planck Analysis Centers, both of which are slated to launch 2007 or 2008 by ESA. Herschel is a far-infrared space observatory covering the window between 157 to 670 um. Planck is a sub-mm/mm (0.33 to 10 mm) survey mission that will map anisotropies in the cosmic microwave background radiation.

IRSA will continue its role in supporting missions that are based at greater-IPAC, including the Herschel/Planck duo. Responsibilities (which are still mostly TBD at this time) include creating web-based tools that may be used by the data centers for mission planning and supporting the development of mission-specific software. It is anticipated that IRSA will work cooperatively with LAMBDA to create a 'distributed CMB data center', wherein LAMBDA possesses the knowledge to investigate the early universe and IPAC the knowledge to investigate the 'foreground' Milky Way and extragalactic universe. This memo describes some of the data products and associated tools that are anticipated to be important for mission planning and operations support.

Existing Tools (relevant to Herschel/Planck)

• IRSKY: Observation Planning Tool for the Infrared Sky; developed by IPAC during the ISO era.

• Galactic Dust Reddening and Extinction: provides cut-outs of IRAS 100 um maps and predicts the Galactic extinction for targets or regions of the sky.

• SCANPI: IRAS Scan Processing and Integration; will visualize, plot and average calibrated IRAS survey scans (particularly useful for estimating an upper limit of the IR background).

• RADAR: IRSA Inventory and Data Mining Service; access to the IRSA data and tools.

• SPOT: Spitzer Tool for Planning Observations. Integrated within SPOT is an IR Background Estimator, developed by Bill Reach (see below).

Data and Tools Needed to Support Planck/Herschel

• COBE-DIRBE maps. Not only are these useful as straight-forward images of the sky (describing the near to far-infrared background), but also as predictors of longer wavelength emission (see below).

• Models to predict the far-infrared and sub-mm/mm background light. The model must account for the location of the spacecraft (Earth for orbiting telescopes like WISE, L2 for Herschel/Planck, and Earth-trailing for Spitzer). Such a model exists for Spitzer, developed by Bill Reach (see link above).

• WMAP: CMB maps covering 23 to 94 GHz (3 to 13 mm). This state-of-the-art data set will ultimately replace COBE as the long-wavelenth baseline of the sub-mm/mm background emission models.

The Ever-growing Use Case File

• What is the Galactic extinction along a line of sight? List the wavelength-dependent extinction.
  
• What is the average extinction for a defined region of the sky?
  
• Line of sight extinction for a table of locations.
  
• What is the dust temperature along a line of sight?
  
• What is the 100 um intensity along a line of sight?
  
• What is the mean 100 um surface brightness for a defined region of the sky?
  
• What is the spatial structure of the far-infrared radiation for a defined region of the sky? Provide an image cut in the specified sky projection.
  
• How does the dust emission compare with the atomic gas column density? Provide images of the far-infrared images and HI images (fr om the Dwingloo HI Survey)
  
• What is the intensity/SB for a region of the sky at sub-mm wavelengths?
  
• How does the far-infrared radiation compare with the CMB from COBE and WMAP? Provide image cut-outs for the dust maps, COBE and WM AP; reproject to a common system.

The COBE data and knowledge thereof resides at LAMBDA. DIRBE (imaging from 1.25 to 240 um) is a particularly useful data product to infrared astronomers. LAMBDA makes DIRBE data products available in Quad-Sphere projection.

As part of creating value-add science products that are useful to IRSA folk (i.e., 'foreground' astronomers), high-level DIRBE products (such as the Annual Average Maps, Sky and Zodi Atlas (DSZA), Zodi-Subtracted Mission Average (ZSMA) Maps, ..., etc) should be converted to more standard TAN projection plates, similar to the IRAS-ISSA and Schlegel et al. atlas that IRSA created and now curates.

These new data products may be served by LAMBDA with seamless access from IRSA web servers, or curated by IRSA with easy access to LAMBDA users (in a practical sense it depends on who wants to take on the lion's share of the work). The DIRBE images may be served through IRSA's RADAR, ATLAS and Galactic Dust Extinction services (as small cut-outs of the sky).

Infrared & Sub/mm Background Emission

The past two decades has seen the coming of all-sky surveys that observed the cosmic background within the near-infrared (COBE, 2MASS), mid/far-infrared (IRAS, COBE, MSX), and the sub-mm/mm (COBE, WMAP) windows. This data enables interpolation between bands to predict the infrared background light, composed of the CIB, galaxies, the Milky Way and interstellar cirrus, and zodiacal light.

Finkbeiner, Davis & Schlegel (1999, ApJ, 524, 867) have developed a method to interpolate their IRAS/DIRBE maps, and extend the models to FIRAS (micro-wave) wavelengths. Specifically, they have produced a 94 GHz map of the sky that traces cold dust emission.

• Microwave Dust Emission with a technical summary given here and the data + software tools are here. Beware of the caveats (see tech summary).

• LAMBA provides a HEALPix version of the Finkbeiner, Davis and Schlegel micro-wave map here.

Spitzer developed (under the direction of Bill Reach) a model that predicts the IR background at Spitzer mid/far-infrared wavelengths, for a spacecraft that is trailing Earth (and hence, observes a time-varying zodical background). This model is extensible to other wavelengths, including infrared and sub/mm.

Spurred by the flexibility of the Reach model, Herschel Scientist Babar Ali and IRSA's John Good created a prototype web-based service that predicts the IR background (at any infrared wavelength) for a given location in space (recall that Spitzer is moving away from earth). The simplicity of the prototype (aka Herschel Background Estimator) suggests that a tool, specific to Herschel and Planck, may be developed by IRSA to support those missions.

Issues: The following notes come from the Galactic Extinction Dust Service science requirements:

• The (Herschel) Background Estimator is needed now by Spitzer users; it will become important to Herschel science observation planners in one to two years. It is now used by the PACS simulator (more precisely, the output from the tool is used by PACS).

• Planck needs the extrapolation to sub-mm wavelengths functionality.

• The Herschel Background Estimator should be generalized to any spacecraft orbit, including those of Spitzer, WISE (Earth), Herschel/Planck.

• The Herschel Background Estimator should include an upload ephemeris functionality.

  More comments from Bill Reach:

• To extrapolate to other wavelengths, you will want either a template spectrum, or a more flexible position-dependent spectrum that somehow uses the IRAS or COBE colors. This latter would be significantly more difficult; I considered it but couldn't justify the great effort (because over most of the sky, the colors are only moderately accurate and are only available in the far-infrared). But as part of the background estimator, you might need to have a more flexible spectral template capability, including maybe a pulldown with different spectral shapes (diffuse ISM, galactic plane, HII region, molecular cloud).

• The background estimator (of which the present service would become a part) would combine the predicted infrared brightness with the zodiacal model. It would also want to include spectra responses of various instruments, and the apertures of them as well. This is obviously a more extensive thing than you have to design right now. For the Schlegel tool, I think you just have to make something that, looking ahead, will easily plug in to the future background estiamtor.

Folding in WMAP CMB data is a longer-term goal of IRSA, as part of its role in supporting Planck and the 'distributed CMB data center'. Issues include creation or modification of existing tools to manipulate HEALPix data products, signal and image extraction (image cut-outs, region statisticss, and micro-wavebackground estimate (see above discussion). TBD TBD TBD ...

Agreement with LAMBDA

IRSA and LAMBDA are now under negotiation to forge an agreement for sharing data and services. Below is the draft IRSA MOU that is under review by LAMBDA:

"IRSA and LAMBDA have agreed to create services that render their mutual archives interoperable. In the first instance, IRSA will develop an image cut-out service that accesses the LAMBDA COBE/DIRBE image archive, extracting regions of the sky requested by the IRSA user. LAMBDA will make their data inventory available to IRSA for this development. Likewise, IRSA will make their meta-data available to LAMBDA on request. Future development will include image-cutout access to the WMAP image archive, and HEALPix indexing of IRSA data products (e.g., 2MASS Point Source Catalog) as a value-add service to LAMBDA's CMB user base."

Links

• IRAS/DIRBE Dust Map Service: Science Requirements

• Galactic Dust Reddening and Extinction

• SIRTF Background Estimation:

• DIRBE/IRAS Dust Maps, the Schlegel et al. web site. The downloadable data is stored in regular FITS, but using a polar projection only (type: GLON-ZEA, GLAT-ZEA)

• CMB Foreground IMages -- LAMBDA data products, including allsky H-alpha maps, HI maps, Galactic REddening (Schlegel et al dust maps)

• Schlegel dust maps (HealPIX FITS) and more served from LAMBDA. Note that the data served here is in HEALPIX format. Here is a description from LAMBDA:
  "Schlegel, Finkbeiner & Davis (see 1998 reference below) derived an all-sky map of Galactic reddening, E(B-V), from a composite 100 micron map formed from IRAS/ISSA maps calibrated using DIRBE observations. This E(B-V) map can be used as an estimator of Galactic extinction.

  The E(B-V) map provided here was constructed using the data and interpolation software distributed by Schlegel & Finkbeiner via their Berkeley mirror website. Specifically, their routine dust_getval was used to interpolate their high resolution dust maps onto pixel centers appropriate for HEALPix Nside=512. The resultant map is in units of magnitudes. Note that the data are undersampled at this pixelization. Additional products are available from the source websites."

• 94GHz Model Dust Map, Using a combination of COBE and IRAS data, Finkbeiner, Davis & Schlegel (1999) derived models for thermal dust emission at microwave and submillimeter frequencies. This map is based on their best-fit two-component Model#8. See more on this extrapolation method here.

• NED Dust Extinction Utility