Planck (spacecraft)

Design and instruments

Planck carried two complementary instruments that together spanned a wide range of frequencies. The Low Frequency Instrument (LFI) used cryogenically cooled radio receivers, while the High Frequency Instrument (HFI) used bolometric detectors operating at very low temperatures. A sophisticated cooling chain — including a sorption cooler and a dilution refrigerator — reduced detector temperatures to fractions of a degree above absolute zero, allowing the observatory to detect minute temperature fluctuations in the CMB.

• Frequency coverage: multiple bands from microwave to submillimetre, enabling separation of CMB signal from foreground emission.
• Angular resolution: finer than previous full-sky surveys, resolving smaller-scale features in the CMB.
• Orbit: Planck operated near the Sun–Earth L2 point for a stable, cold observing environment.

Mission timeline and operations

After launch, commissioning and calibration took several months before routine sky surveys began. The mission operated actively through the early 2010s; the HFI ceased active observations when its cryogen supply was exhausted, after which LFI continued until the spacecraft was decommissioned. Data were released to the scientific community in staged catalogues and maps, including major public releases that enabled detailed cosmological analysis and follow-up studies by astronomers worldwide. For mission details see the official mission pages and summaries (mission overview, data products).

Key scientific results

Planck produced the most precise measurements of the CMB temperature anisotropies and a high-quality map of CMB polarization. These results constricted models of the early Universe, tested inflationary scenarios, and provided tight estimates of cosmological parameters. Notable outcomes include refined values for the total matter density, the baryon fraction, and the age of the Universe (commonly quoted as about 13.8 billion years). Planck also measured the spectral index of primordial fluctuations and placed limits on departures from Gaussian initial conditions, influencing theories of cosmic structure formation (cosmology, astrophysics).

Legacy and notable facts

Planck set a new standard for full-sky CMB observations and remains a primary reference for precision cosmology. Its datasets continue to be used for cross-correlation studies with large-scale structure, measurements of galactic foregrounds, and tests of fundamental physics. The mission helped sharpen discussions about remaining tensions in cosmological measurements—such as comparisons of the Hubble constant from early- versus late-Universe probes—and left a comprehensive archive of maps, power spectra, and simulations for future research (matter density, dark matter, age of the Universe).

Further reading and data access can be found through the project's public pages and scientific publications (mission overview, ESA, data products, comparisons, cosmology summaries, astrophysics results, baryon measurements, dark matter constraints, age estimates).