Planck Mission Explained: Mapping the Cosmic Microwave Background

Planck Mission — Mapping the Cosmic Microwave Background

Launched: 14 May 2009 (Ariane 5, shared with Herschel).
Orbital location: Lissajous orbit around Sun–Earth L2 (~1.5 million km from Earth).
Instruments: two detectors — Low Frequency Instrument (LFI, 30–70 GHz) and High Frequency Instrument (HFI, 100–857 GHz); 1.5 m telescope; cryogenically cooled detectors.
Primary goal: produce the most precise all‑sky maps of the cosmic microwave background (CMB) temperature and polarization to measure early‑Universe physics and cosmological parameters.

Key achievements and results

Full‑sky CMB maps released in stages: first maps/public data 2010–2011, major cosmology release March 2013, polarization/expanded release February 2015, final papers July 2018.
Precisely measured cosmological parameters: age of the Universe ≈ 13.8 billion years; matter/energy composition (ordinary matter ≈ 4.8–4.9%, dark matter ≈ 26–27%, dark energy ≈ 69%); H0 ≈ 67–68 km·s⁻¹·Mpc⁻¹ (Planck’s value, lower than some local measurements).
High-resolution temperature and polarization maps constrained inflation models, supported the standard ΛCDM cosmology, and reduced parameter uncertainties substantially vs. WMAP.
Produced extensive legacy products: nine‑band frequency maps (foreground separation), compact‑source catalogs including Sunyaev–Zel’dovich (SZ) cluster catalogs, Galactic dust polarization maps, and CMB lensing maps.
Revealed and quantified “anomalies” (large‑scale isotropy deviations) that remain topics of study.

Why it mattered

Improved angular resolution and sensitivity over predecessors (COBE, WMAP) and broader frequency coverage allowed far better separation of Galactic/foreground emission from the primordial CMB signal.
Set the observational precision baseline for modern cosmology and provided a public legacy dataset used across astrophysics (structure formation, Galactic science, extragalactic sources).