Surace Cal Summit III Jason Surace April 19, 2007 Spitzer-IRAC/Akari-IRC Cross-Calibration With figures by Ohyama, Wada, and Tanabe

Surace Cal Summit III Our Interest in Akari (formerly Astro-F, formerly IRIS) It is in the overall interest of IRAC to ensure that the calibration of Akari is consistent with IRAC’s. This will allow direct comparison between datasets on both satellites, and along the way ensure we haven’t made any major errors. IRC has capabilities Spitzer doesn’t. It has more broadband filters, and spectroscopic capabilities down to 1.5 µm.

Surace Cal Summit III Brief Akari Overview Much like Spitzer: 68 cm telescope, this satellite is not small! 4m long, 960kg! Imaging and Spectroscopy

Surace Cal Summit III Sun-synchronous Earth orbit 68cm telescope 3.7m, 960kg 170l He, 1.8 yrs µm Primarily all-sky survey Earth-trailing Solar orbit 86cm telescope 4.4m, 950 kg 350l He, 5.5 yrs µm Primarily pointed observations

Surace Cal Summit III IRC and FIS 10x10’ imaging 2,3,4,7,9,11,15,18,24,6 0,160µm Low-res slit and slitless spectroscopy over entire wavelength range IRAC, IRS, and MIPS 5x5’ imaging ~4,5,6,8,24,70,160 µm, plus some minimal 16µm Low and high-res slit spectroscopy over 5-40µm Low-res spectroscopy µm

Surace Cal Summit III Post-Cryo! Spitzer: IRAC 3.6 and 4.5µm channels will continue working. Passive cooling. Akari: IRC NIR channel, with 2, 3, 4µm filters plus spectroscopy will continue to work. Passive cooling plus cryo-coolers.

Surace Cal Summit III Equivalent of JPL+Goddard Runs all space science missions (I.e. everything). Development, assembly, operations, research, etc. 250 total people. Akari looks to be operated by people, total.

Surace Cal Summit III

Summary on IRC Spectroscopy Capability CameraDisperser Name Array FOV (arcmi n 2 ) Pix scale (arcse c /pix) ID Type  (µm)  d Spec. Lengt h NIR InSb 512 X ' X10.0' 1.46” NP prism 1.8– µm 81 pix NG grism 2.5– µm 261 MIR-S Si:As 256 X ' X10.0' 2.34” SG1 grism 5.3– µm 85 SG2 grism 7.5– µ m 91 MIR-L Si:As 256 x ' X10.2' 2.51” x2.39” LG1 grism 11– 14.4µ m --- LG2 grism 17.7 – µ m 79 IRC Spectroscopic Capabilities

Surace Cal Summit III NIR N2 ( µm) single1-min observation ~10 min stack

Surace Cal Summit III NIR (InSb) NP Prism (2-6µm)

Surace Cal Summit III MIR-L Si:As LG2 Grism (17-25µm)

Surace Cal Summit III Akari Calibrator Stars Akari calibration methodology identical to IRAC’s. Martin Cohen generates predicted fluxes based on instrument throughput and templates. Broad-band imaging and spectroscopy both calibrated in this fashion. Almost all Akari calibrators already observed by IRAC. Mostly A & K-stars. Deliberate overlap with IRAC to extent allowed by pointing constraints.

Surace Cal Summit III Some Difficulties Difficult to use the slits due to pointing issues. Advantages to using slitless (easier to handle slit loss), but there are confusion problems at short wavelengths. Also, wavelength calibration not fixed and leads to problems near spectrum ends.

Surace Cal Summit III Black is Cohen template, blue is IRC data. 2MASS KF06T2 - K-star Note - calibration is set by this object at short end. Near-IR Prism

Surace Cal Summit III BP K-star HD A-star (calibrator) KF09T1 K-star Near-IR Grism

Surace Cal Summit III K vs. A (in mJy*um^2 unit) KA KF06T2 2MASS

Surace Cal Summit III K vs. A (in mJy*um^2 unit) KA

Surace Cal Summit III Unfortunately, this is confused by the fact that we don’t have the raw spectra, only the flux-calibrated ones which already have the standard star response in them. But you can see the absorption trough in channel 2 easily!

Surace Cal Summit III K vs. A (in mJy*um^2 unit) KA

Surace Cal Summit III Mid-IR Short Grism 1 BP K-star HD A-star (calibrator) NPM 1p K-star

Surace Cal Summit III Mid-IR Short Grism 2 BP K-star HD A-star (calibrator)

Surace Cal Summit III Are We Learning Anything? For at least some K-stars, Martin’s templates have too deep troughs. But they work well for other stars. Inadequacy of optical spectral typing? No obvious surprise features. Still need to get raw data. Getting any data has been tricky.

Surace Cal Summit III Akari Calibration Locations Akari CVZ within 0.6 degrees of ecliptic pole (similar to WISE), vs. 4-5 for Spitzer. All Akari cal stars located within their northern and southern CVZ. Deep survey at ecliptic caps. Ideal for general cross-cal with IRAC. IRAC dark field outside the Akari CVZ, although it is being observed in a fashion as part of a mission project (Egami, PI). Observing Akari cal field as an IRAC cal activity.

Surace Cal Summit III “Deep” Component Central 5x5’ Depth is 28x100 seconds 5-sigma = 0.6, 1.2, 7.5, and 9 µjy at 3.6, 4.5, 5.8, and 8 µm. Confusion-limited at 3.6 and 4.5µm. 2 hours to execute.

Surace Cal Summit III “Shallow” Component Coverage of a 10x10’ area with all 4 arrays. 8x30 seconds = 2x SWIRE integration time 5-sigma = 2.5, 4.2, 28, and 32µJy at 3.6, 4.5, 5.8, 8 µm. High Dynamic Range Mode 50 minutes to execute

Surace Cal Summit III Akari NEP Cal Field Observed by IRAC Ch.1 Entire Field, all exposures Ch.1 Ch.4

Surace Cal Summit III IRAC vs. IRC Broadband Photometry

Surace Cal Summit III Early Results from Cross-Cal Field Encouraging Computed the expected slopes from Martin’s model calculations for specific stars. IRC/IRAC numbers match to within 5%, the limit I could measure them to. Somewhat circular, since Akari also calibrated to Cohen templates. Indicates no significant issues with system throughput measurements. Indicates that point source measurement and calibration methodology holds and agrees between missions.