Slide 2
Artist's conception of the COBE satellite in orbit, annotated with locations of scientific instruments, dewar, etc.

Slide 3
The COBE orbit and spin axis orientation. The orbit nearly passes over the Earth's poles at an altitude of 900 km (559 miles).

Slide 4
DIRBE optical concept showing mirrors, filters, detectors, and beam interrupter. The DIRBE uses an unobscured off-axis Gregorian telescope to collect light and bring it to a focus on 16 infrared detectors.

Slide 5
DIRBE test unit showing optics and copper straps used to keep detectors cold. Optics were surrounded with baffle tubes to stop stray light.

Slide 6
DIRBE scan track superposed on 100 µm Annual Average Map and 100 µm intensity from the corresponding segment of time-ordered data. DIRBE scanned the sky in a helical pattern that resulted from the spin and orbital motion of the COBE satellite and the "look direction" of the telescope, which was 30 degrees from the spin axis.

Slide 7
100 µm Weekly Sky Maps for mission weeks 4 to 44, and the 100 µm Annual Average Map. Shows sky coverage each week of the DIRBE mission over the period during which the COBE cryogen supply lasted.

Slide 8
Annual Average Maps at 3.5, 25, 100, and 240 µm. Galactic coordinate Mollweide projection maps of the entire sky at four wavelengths showing emission from stars and dust in the Galactic plane (horizontal feature) and light scattered and emitted by dust in the solar system (S-shape).

Slide 9
1.25, 2.2, and 3.5 µm Solar elongation angle = 90 degree Maps. Galactic coordinate Mollweide projection maps of the entire sky as seen by the DIRBE at a fixed angle relative to the Sun. Stars concentrated in the Galactic plane (horizontal feature) dominate the images at these wavelengths.

Slide 10
False-color image of the near-infrared sky as seen by the DIRBE. Data at 1.25, 2.2, and 3.5 µm wavelengths are represented respectively as blue, green and red colors. The image is presented in Galactic coordinates, with the plane of the Milky Way Galaxy horizontal across the middle and the Galactic center at the center.

Slide 11
1.25, 2.2, 3.5 µm composite image of Galactic center region. Shows asymmetric shape of the bulge at the center of the Milky Way. The image is a Mollweide projection covering 60 degrees in Galactic longitude by 20 degrees in Galactic latitude and centered on the Galactic center.

Slide 12
4.9, 12, 25, and 60 µm Solar elongation angle = 90 degree Maps. Thermal emission from star-heated dust in the Milky Way and interplanetary dust heated by the Sun dominates the images at these wavelengths.

Slide 13
This image combines data from the DIRBE obtained at infrared wavelengths of 4.9, 12 and 25 µm. The sky brightness at these wavelengths is represented respectively by blue, green, and red colors in the image.

Slide 14
This image combines data from the DIRBE obtained at infrared wavelengths of 25, 60 and 100 µm. The sky brightness at these wavelengths is represented respectively by blue, green, and red colors in the image. The plane of the Milky Way Galaxy lies horizontally across the middle of the image with the Galactic center at the center.

Slide 15
100, 140, and 240 µm Solar elongation angle = 90 degree Maps. Thermal emission from relatively cool interstellar dust warmed by stars in the Milky Way dominates at these wavelengths. At high Galactic latitudes, interstellar "cirrus" clouds are apparent.

Slide 16
DIRBE 1.25 and 2.2 µm maps of the sky as observed (top) and following subtraction of a detailed model of the zodiacal light (middle and bottom), which at these wavelengths is Sunlight scattered by interplanetary dust grains.

Slide 17
DIRBE 3.5 and 4.9 µm maps of the sky as observed (top) and following subtraction of a detailed model of the zodiacal light (middle and bottom).

Slide 18
DIRBE 12 and 25 µm maps of the sky as observed (top) and following subtraction of a detailed model of the zodiacal light (middle and bottom), which at these wavelengths is thermal emission from interplanetary dust grains heated by absorbed Sunlight (see Kelsall et al. 1998, ApJ, 508, 44).

Slide 19
DIRBE 60 and 100 µm maps of the sky as observed (top) and following subtraction of a detailed model of the zodiacal light (middle and bottom), which at these wavelengths is thermal emission from interplanetary dust grains heated by absorbed Sunlight (see Kelsall et al. 1998, ApJ, 508, 44).

Slide 20
DIRBE 140 and 240 µm maps of the sky as observed (top) and following subtraction of a detailed model of the zodiacal light (middle and bottom; see Kelsall et al. 1998, ApJ, 508, 44).

Slide 21
At near-infrared wavelengths, following the subtraction of zodiacal light (see Slide 16), map pixels containing discrete bright sources are masked and the DIRBE Faint Source Model is used to subtract residual Galactic starlight in order to detect or place an upper limit on the brightness of the cosmic infrared (extragalactic) background emission (Arendt et al. 1998, ApJ, 508, 74).

Slide 22
Results of the DIRBE search for the Cosmic Infrared Background (CIB) after removal of foreground emissions from the solar system and the Milky Way (see Hauser et al. 1998, ApJ, 508, 25).

Slide 23
An illustration of the foreground emission subtraction process resulting in the DIRBE detection of the Cosmic Infrared Background at 240 µm. The map at the top is a false-color image showing the observed infrared sky brightness at wavelengths of 60 (blue), 100 (green) and 240 µm (red).

Slide 24
This image combines data from the DIRBE obtained at infrared wavelengths of 100, 140 and 240 µm - the longest wavelengths measured by this instrument. The sky brightness at these wavelengths is represented respectively by blue, green, and red colors in the image.

Slide 25
Signal flow in the DMR instrument, which was designed to detect and enable the characterization of temperature differences ("anisotropy") in the cosmic microwave background radiation. The DMR design is similar to that used in instruments flown on balloons and aircraft. The receiver input is connected alternately to two separate antennas that point at different parts of the sky.

Slide 26
The 9.6 mm DMR receiver partially assembled.

Slide 27
Early DMR sky maps depicting data obtained from the independent ("A" and "B") channels at each of the three observed microwave wavelengths: 3.3, 5.7 and 9.6 mm (corresponding frequencies are 90, 53 and 31.5 GHz, or thousand MHz, respectively).

Slide 28
Following subtraction of the dipole anisotropy and components of the detected emission arising from dust (thermal emission), hot gas (free-free emission), and charged particles interacting with magnetic fields (synchrotron emission) in the Milky Way Galaxy, the cosmic microwave background (CMB) anisotropy can be seen.

Slide 29
Maps based on 53 GHz (5.7 mm wavelength) observations made with the DMR over the entire 4-year mission (top) on a scale from 0 - 4 K, showing the near-uniformity of the CMB brightness, (middle) on a scale intended to enhance the contrast due to the dipole described in the slide 19 caption, and (bottom) following subtraction of the dipole component. Emission from the Milky Way Galaxy is evident in the bottom image.

Slide 30
Maps based on observations made with the DMR over the entire 4-year mission, at each of the three measured frequencies, following dipole subtraction. See slide 19 caption for information about map smoothing and projection.

Slide 31
The 53 GHz DMR sky map (top) prior to dipole subtraction, (middle) after dipole subtraction, and (bottom) after subtraction of a model of the Galactic emission, based on data gathered over the entire 4-year mission.

Slide 32
DMR "Map of the Early Universe." This false-color image shows tiny variations in the intensity of the cosmic microwave background measured in four years of observations by the Differential Microwave Radiometers on NASA's Cosmic Background Explorer (COBE).

Slide 33
Concept of FIRAS, showing light from the sky being focused through cone and sent to interferometer. The FIRAS instrument was designed to measure precisely the spectrum of the cosmic microwave background radiation over a wavelength range from 0.1 to 10 mm.

Slide 34
FIRAS test unit being prepared for vibration test. Horn, calibrator, and mirror mechanism are not shown.

Slide 35
FIRAS horn antenna with movable calibrator. Protective plastic covers were removed before launch.

Slide 36
Cosmic microwave background (CMB) spectrum. The solid curve shows the expected intensity from a single temperature blackbody spectrum, as predicted by the hot Big Bang theory.

Slide 37
FIRAS measured cosmic microwave background radiation residual spectrum from Mather et al. 1994, ApJ, 420, 439.

Slide 38
C+ 158 µm and N+ 205 µm line intensity maps from Fixsen et al. 1999, Astrophysical Journal, 526, 207,"COBE Far Infrared Absolute Spectrophotometer Observations of Galactic Lines" . The maps are projections of the full sky in Galactic coordinates. Note: The images from 1999 are based on combined destriped data with higher frequency resolution from the FIRAS Pass4 data release.

Slide 39
FIRAS map of N+ 205 µm spectral line intensity. (See slide 38 caption.)

Slide 40
A map of the temperature of interstellar dust in the Milky Way Galaxy derived from FIRAS sub-millimeter data. The map is a projection of the full sky in Galactic coordinates. The plane of the Milky Way is horizontal in the middle of the map with the Galactic center at the center.