We have reÐned the analysis of the data from the FIRAS (Far-InfraRed Absolute Spectrophotometer) on board the COBE (COsmic Background Explorer). The FIRAS measures the di †erence between the cosmic microwave background and a precise blackbody spectrum. We Ðnd new, tighter upper limits on general deviations from a blackbody spectrum. The rms deviations are less than 50 parts per million of the peak of the cosmic microwave background radiation. For the Comptonization and chemical potential, we Ðnd o y o \ 15 ] 10~6 and o k o \ 9 ] 10~5 (95% conÐdence level [CL]). There are also reÐne-ments in the absolute temperature, 2.728^0.004 K (95% CL), the dipole direction, (l, b) \ (264¡ .14 0.30, (95% CL), and the amplitude, 3.372^0.014 mK (95% CL). All of these results 48¡ .26^0.30) agree with our previous publications.

The COBE FIRAS data contain foreground emission from interplanetary, Galactic interstellar dust and extragalactic background emission. We use three different methods to separate the various emission components, and derive the spectrum of the extragalactic Far InfraRed Background (FIRB). Each method relies on a different set of assumptions, which affect the FIRB spectrum in different ways. Despite this, the FIRB spectra derived by these different methods are remarkably similar. The average spectrum that we derive in the ν = 5 − 80 cm −1 (2000 -125 µm) frequency interval is:, where ν 0 = 100 cm −1 (λ 0 = 100 µm) and P is the Planck function. The derived FIRB spectrum is consistent with the DIRBE 140 and 240 µm detections. The total intensity received in the 5 -80 cm −1 frequency interval is 14 nW m −2 sr −1 , and comprises about 20% of the total intensity expected from the energy release from nucleosynthesis throughout the history of the universe.

The Far InfraRed Absolute Spectrophotometer data are independently recalibrated using the Wilkinson Microwave Anisotropy Probe data to obtain a cosmic microwave background (CMB) temperature of 2.7260 ± 0.0013. Measurements of the temperature of the CMB are reviewed. The determination from the measurements from the literature is CMB temperature of 2.72548 ± 0.00057 K.

The Infrared Array Camera (IRAC) is one of three focal plane instruments in the Spitzer Space Telescope. IRAC is a four-channel camera that obtains simultaneous broad-band images at 3.6, 4.5, 5.8, and 8.0 µm. Two nearly adjacent 5.2×5.2 arcmin fields of view in the focal plane are viewed by the four channels in pairs (3.6 and 5.8 µm; 4.5 and 8 µm). All four detector arrays in the camera are 256×256 pixels in size, with the two shorter wavelength channels using InSb and the two longer wavelength channels using Si:As IBC detectors. IRAC is a powerful survey instrument because of its high sensitivity, large field of view, and four-color imaging. This paper summarizes the in-flight scientific, technical, and operational performance of IRAC.