PACE (Plankton, Aerosol, Cloud, ocean Ecosystem)

The first hyperspectral ocean-color mission + the first NASA mission with two complementary polarimeters. PACE replaces MODIS-Aqua and SeaWiFS heritage with a fundamentally new spectral capability — 200+ contiguous bands across the ocean-color spectrum, plus angular + polarized aerosol/cloud sensing.

What it sees

• OCI: hyperspectral 340–895 nm at 5 nm sampling (continuous), plus 9 SWIR bands. 1 km nadir resolution; 2660 km swath. Replaces and exceeds MODIS Aqua ocean color, with finer spectral fidelity for phytoplankton-type discrimination and dissolved-organic-matter retrieval.
• HARP2: multi-angle (60 angles), multi-band (4 bands) polarimeter. Sees clouds + aerosols from 60 viewpoints — constrains aerosol size, shape, refractive index, height.
• SPEXone: 5 viewing angles, hyperspectral polarimetry from 385–770 nm. High-precision aerosol microphysics.

Why it matters

• Closes the spectral gap that prevented discrimination between phytoplankton functional types — diatoms vs cyanobacteria vs picoeukaryotes — from space. This is the biggest ocean-biology advance since SeaWiFS in 1997.
• Aerosol microphysics from polarimetry is a step-change for radiative-forcing science — knowing aerosol size + composition, not just optical depth.
• Coastal waters (Case II) — PACE’s hyperspectral OCI handles complex coastal water types (CDOM-rich, sediment-rich) better than MODIS’s broad bands could.
• Baynes cited PACE OCI specifically in 2024 program highlights — high visibility within NASA leadership.

Where to get the data

• earthaccess Python: short_name="PACE_OCI_L2_OC_NRT" (NRT ocean color), PACE_OCI_L2_SFREFL_NRT (atmospheric correction), PACE_OCI_L3M_CHL (gridded chlorophyll)
• OB.DAAC OceanColor Web: oceancolor.gsfc.nasa.gov — browse + download
• PACE Data Portal: pace.oceansciences.org/data.htm
• PACE Hackweek 2025 materials: pace.oceansciences.org/events_more.htm?id=73 (tutorials + worked examples)

What it enables

• Phytoplankton community composition — not just “is there chlorophyll” but “what kind of algae”
• Harmful Algal Bloom (HAB) detection — cyanobacteria signatures in lakes + coastal waters
• Aerosol-cloud-precipitation interactions — polarimetric retrievals constrain microphysics for climate models
• Coastal water quality at higher spectral fidelity than MODIS
• Mineral dust transport (Sahara → Caribbean, Asian dust → North America) — polarimetric size constraints
• Phytoplankton phenology for fisheries + carbon-cycle science

Gotchas

• Brand new (operational since April 2024) — tutorial ecosystem still maturing. PACE Hackweek 2025 was a major build-out moment.
• Hyperspectral data volume is large — OCI L1B granules are 1+ GB each. Plan storage.
• Atmospheric correction over Case-II coastal waters is hard. Don’t blindly trust standard SeaWiFS-era algorithms; PACE has new approaches but they’re still being validated.
• HARP2 and SPEXone are complementary, not redundant. HARP2 is wide-swath, lower precision; SPEXone is narrow-swath, high precision. Don’t substitute one for the other.
• The hyperspectral revolution requires new processing. SeaWiFS / MODIS pipelines that worked on 9 bands don’t translate; you need 285-band-aware algorithms.

Related missions

• MODIS Aqua (s04 →): ocean-color heritage — PACE supersedes for science but Aqua continues for continuity through ~2027.
• VIIRS (s05 →): operational ocean-color continuity (multispectral, not hyperspectral).
• GLIMR (Geostationary Littoral Imaging and Monitoring Radiometer): planned GEO ocean-color mission ~2027.
• GOCI-II (Korean GEO ocean color over East Asian seas).

Related datasets