Start with the dataset you use today. The table below gives a practical first choice and the expected amount of workflow change; verify product-level details before switching.

NetCDF-based files, familiar geophysical quantities, and Level-2/Level-3 concepts remain recognizable across many products. The items below are the parts most likely to require code or science-review changes.

Important Scientific Continuity Note 

Corresponding products across missions represent the same geophysical quantities and are intended to support continuity. For applications sensitive to small cross-sensor differences—such as long-term trends or climate studies—sensor characteristics, calibration, sampling, processing versions, and algorithm implementation differences may still warrant evaluation.

PACE OCI — Continue Familiar Products and Expand Capability

PACE OCI carries forward familiar ocean-color quantities such as chlorophyll-a, Rrs, Kd, IOPs, POC, PIC, and PAR, while adding hyperspectral observations and broader optical, biogeochemical, and ecosystem products. OCI's tilt strategy can reduce sunglint impacts and improve usable coverage, and current processing incorporates updated atmospheric-correction approaches. For standard-product users, the main workflow changes are PACE's broader science suites (for example AOP and BGC) and, for spectral products, hyperspectral wavelength handling. Expanded examples include spectral optical properties, phytoplankton carbon, MOANA phytoplankton community composition, and NPP_CAFE primary productivity. 

Note: This table highlights selected expanded PACE mapped products rather than a complete product inventory. See the PACE Data Products Overview for current availability and processing status.

Useful references:

• PACE Data Products Overview
• PACE mission overview
• OCI instrument overview
• PACE OCI Version 3 Release Notes

NOAA-20/21 VIIRS — Minimize Workflow Changes

NOAA-20/21 VIIRS provides the lowest-friction path for many established MODIS and Suomi NPP VIIRS products. The transition is especially straightforward for Suomi NPP VIIRS users because the instrument family, variable conventions, and product organization are similar. Users should still verify wavelengths, algorithm details, and processing versions for quantitative cross-sensor work.

Useful references:

• VIIRS instrument overview
• NOAA-20 platform
• NOAA-21 platform
• NASA ARSET: Monitoring Coastal and Estuarine Water Quality — Transitioning from MODIS to VIIRS

Sentinel-3A/B OLCI — Level-3 Continuity With an Optional Higher-Resolution Level-2 Path

Sentinel-3A and Sentinel-3B carry the Ocean and Land Colour Instrument (OLCI), a current multispectral option available through NASA Earthdata. For users continuing an existing Level-3 mapped workflow, OLCI Level-3 ERR products provide the corresponding mapped-product option for supported product families.

Users who specifically need finer spatial detail can separately consider OLCI Level-2 Full Resolution (EFR, approximately 300 m). EFR is a geolocated swath product and represents a different Level-2 workflow rather than a direct replacement for an existing Level-3 mapped workflow. Use EFR when approximately 300 m spatial detail is important, for example in estuaries, lakes, river plumes, coastal fronts, and other spatially complex waters. Latitude and longitude are provided with the Level-2 swath; users whose downstream analysis expects a regular grid may need swath-aware reading and mapping/regridding or aggregation.

Standard Level-3 mapped OLCI products are based on the ERR stream and are available at coarser mapped resolutions such as 4 km and 9 km. These are the appropriate OLCI products to compare with existing Level-3 mapped workflows; selecting a Level-3 product does not provide the approximately 300 m EFR resolution.

Current full-resolution Level-2 ocean-color collections:

• Sentinel-3A: OLCIS3A_L2_EFR_OC
• Sentinel-3B: OLCIS3B_L2_EFR_OC

Useful references:

• OLCI instrument overview
• Sentinel-3A platform
• Sentinel-3B platform
• NASA Water Quality Products Fact Sheet
• Wekeo Learn OLCI — hands-on Sentinel-3 OLCI Level-1B/Level-2 notebooks (external resource linked from Help Hub)

Identify the product and processing level used in the current workflow, then locate the corresponding current product family from PACE OCI, NOAA-20/21 VIIRS, or Sentinel-3A/B OLCI.

The crosswalk below focuses on commonly used Level-3 mapped products and is not exhaustive. Collection names link directly to their Earthdata Search records. If your workflow uses a product not shown here, use the mission product documentation to identify the current collection and migration considerations.

Crosswalk note: Product-family matches identify corresponding products across missions. Sensor-specific differences may still matter for applications sensitive to cross-sensor consistency. See Building a scientifically consistent multi-sensor time series below.

Remote Sensing Reflectance (Rrs)

What changes? Rrs remains the same geophysical quantity, but the available wavelengths differ by sensor. MODIS, VIIRS, and OLCI provide discrete multispectral bands, while PACE OCI provides hyperspectral Rrs. Scripts that select specific wavelengths or hard-code Rrs <wavelength> variables should therefore be reviewed.

Algorithm documentation: Rrs ATBD

Chlorophyll-a (chlor_a)

What changes? chlor_a remains the same geophysical product across missions. The algorithm uses sensor-specific spectral bands and associated coefficients, while PACE OCI also changes the collection organization by distributing chlor_a within the broader BGC suite.

Algorithm documentation: Chlorophyll-a ATBD

Diffuse Attenuation (Kd)

What changes? Heritage MODIS and VIIRS products provide Kd_490, derived with the empirical KD2 algorithm. PACE OCI provides spectral Kd(λ), derived from IOPs using the Lee et al. (2005) semi-analytical model. Users extending a Kd_490 workflow into PACE should therefore verify the wavelength and algorithm.

Algorithm documentation: Heritage Diffuse Attenuation ATBD • PACE Spectral Kd ATBD • Lee et al. (2005)

Inherent Optical Properties (IOPs)

What changes? The same core IOP quantities—including absorption and backscattering products—continue across missions, but their available wavelengths differ by sensor. PACE OCI extends the spectral sampling of several IOPs, so users should check individual variable names and wavelengths rather than assume a one-to-one band match.

Algorithm documentation: IOP ATBD

Particulate Organic Carbon (POC)

What changes? POC remains the same geophysical product and units across these missions, while the sensor-specific algorithm implementation differs. Current MODIS/VIIRS POC uses the heritage 443/555 blue-to-green band-ratio implementation, while PACE OCI uses the Stramski et al. (2022) hybrid algorithm.

Algorithm documentation: Heritage POC ATBD • PACE POC ATBD • Stramski et al. (2022) • PACE OCI BGC validation

POC Continuity Note

Current heritage product metadata identifies POC as “D. Stramski, 2007 (443/555 version)”; the method was published in final peer-reviewed form as Stramski et al. (2008). PACE OCI uses the 2022 hybrid implementation. For applications sensitive to small cross-sensor differences, users may wish to evaluate overlap-period consistency when extending a quantitative POC record into PACE.

Particulate inorganic carbon (PIC)

What changes? PIC remains available from VIIRS and PACE OCI. VIIRS provides dedicated Level-3 PIC collections, while PACE distributes PIC within the BGC suite.

Algorithm documentation: PIC ATBD

Photosynthetically Available Radiation (PAR)

What changes? The standard daily PAR product remains available as a Level-3 mapped product for VIIRS and PACE OCI. For most users, the main transition is therefore the mission and collection identifier rather than the geophysical product itself.

Algorithm documentation: PAR ATBD

These examples use real collection short names to show the kinds of changes a script actually needs. They are representative rather than exhaustive; use the crosswalk above for other products.

Before changing a production workflow, retrieve at least one representative file from the target collection and verify dimensions, variables, fill values, metadata, quality flags, and the resulting analysis output.

Corresponding MODIS, VIIRS, OLCI, and OCI products are designed to support mission-to-mission continuity. For many applications, they can be used directly across missions. However, applications sensitive to small cross-sensor differences—such as long-term trends, climate studies, or algorithm development—may require additional evaluation.

Consider differences in:

• Spectral response and calibration
• Spatial and temporal sampling
• Atmospheric correction
• Sensor-specific algorithms or coefficients
• Processing versions and cross-sensor biases

Where missions overlap, comparing the records can help characterize biases and uncertainties before combining them. For long-term multi-mission analyses, an established harmonized product may also be appropriate.

Earthdata Search

The collection links throughout this guide open the corresponding datasets directly in NASA Earthdata Search.

Use Earthdata Search to:

• Review collection metadata
• Select temporal and geographic ranges
• Discover available granules
• Access data
• Review related documentation and resources

Automated Discovery with CMR

If your scripts query CMR directly, migration often requires updating the collection short name. A useful approach is to query the collection record first, inspect the returned collection version and concept ID, and then use the selected collection concept ID for granule searches when you want to target that specific collection. This avoids unnecessarily hard-coding a collection version into the discovery workflow.

Example 1 — Suomi NPP VIIRS Chlorophyll → NOAA-20/21 VIIRS

Before:
https://cmr.earthdata.nasa.gov/search/collections.json?short_name=VIIRSN_L3m_CHL

NOAA-20:
https://cmr.earthdata.nasa.gov/search/collections.json?short_name=VIIRSJ1_L3m_CHL

NOAA-21:
https://cmr.earthdata.nasa.gov/search/collections.json?short_name=VIIRSJ2_L3m_CHL

Example 2 — Chlorophyll → PACE OCI

PACE OCI chlorophyll is distributed as chlor_a within the BGC product suite rather than in a separate chlorophyll collection.

First, locate the PACE OCI BGC collection:

https://cmr.earthdata.nasa.gov/search/collections.json?short_name=PACE_OCI_L3M_BGC

Then search for granules within the desired time range. For example:

https://cmr.earthdata.nasa.gov/search/granules.json?short_name=PACE_OCI_L3M_BGC&temporal=2026-03-05T00:00:00Z,2026-03-06T23:59:59Z

This query returns PACE OCI BGC granules whose temporal coverage overlaps the specified period. Because the collection includes multiple temporal composites and mapped resolutions, the results may include daily as well as longer-period composite granules.

For more explicit collection targeting in automated workflows, resolve the desired collection first and use its returned concept ID in the granule query:

.../search/granules.json?collection_concept_id=<collection_concept_id>&temporal=<start>,<end>

CMR supports both short_name and parent collection concept ID for granule searches; using the concept ID explicitly targets the selected collection. Add a version constraint only when the workflow intentionally needs a specific collection version. 

Reference: NASA Common Metadata Repository (CMR) Search API documentation.

Related Help Hub Tutorials

These tutorials complement the migration guidance above with hands-on examples for data discovery, file structure, version changes, and, where relevant, optional Level-2 swath processing.

• Access Data from OCI — search and retrieve data with earthaccess/CMR; the same search pattern can be adapted to other Earthdata collections.
• Explore Level-3 MODIS Ocean Color Data — a practical baseline for MODIS Level-3 discovery, download, and analysis with earthaccess.
• Data Structure at Three Processing Levels for OCI — compare OCI NetCDF groups, dimensions, and variables across L1B, L2, and L3M.
• Science Data Reprocessing and Product Versions — understand processing-version, collection-name, and file-structure changes that can affect existing code.
• Projecting PACE Data onto a Predefined Grid — useful background for users who independently choose a Level-2 swath workflow and need to work with provided latitude/longitude information, quality masking, and re-gridding.

Product and Algorithm Documentation

The ATBD and algorithm links in the product crosswalk above provide documentation for the corresponding products and retrieval approaches.

A common product or variable name identifies the same geophysical product, although sensor-specific algorithm implementations or coefficients may differ. Review the linked ATBDs when those implementation details matter for the scientific application. Mission and instrument links are provided in the transition sections above.

Need Help?

For questions about selecting or transitioning ocean color datasets:

• Oceandata Help Hub
• Earthdata Forum
• Mission-specific Earthdata collection pages

Scientific Literature

• Werdell, P. J., Behrenfeld, M. J., Bontempi, P. S., Boss, E., Cairns, B., Davis, G. T., Franz, B. A., Gliese, U. B., Gorman, E. T., Hasekamp, O., Knobelspiesse, K. D., Mannino, A., Martins, J. V., McClain, C. R., Meister, G., & Remer, L. A. (2019). “The Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) mission: Status, science, advances.” Bulletin of the American Meteorological Society, 100(9), 1775–1794. doi: 10.1175/BAMS-D-18-0056.1
• Werdell, P. J., Cairns, B., Caplan, S. A., Cetinić, I., Foley, S. R., Franz, B. A., Gao, M., Fasnacht, Z. T., Huemmrich, K. F., Ibrahim, A., Knobelspiesse, K. D., Mannino, A., McKinna, L. I. W., Poulin, C., Rajapakshe, C., & Sayer, A. M. (2026). “Advancing Earth System Science With the NASA Plankton, Aerosol, Cloud, Ocean Ecosystem (PACE) Satellite Mission.” Global Change Biology, 32(4), e70869. doi: 10.1111/gcb.70869
• Paulino, R. S., Martins, V. S., Caballero, C. B., Lima, T. M. A., Liu, B., Ashapure, A., & Werdell, P. J. (2026). “PACE (Plankton, Aerosol, Cloud, ocean Ecosystem): Preliminary analysis of the consistency of remote sensing reflectance product over aquatic systems.” ISPRS Journal of Photogrammetry and Remote Sensing, 232, 196–209. doi: 10.1016/j.isprsjprs.2025.12.003
• Franz, B. A., Werdell, P. J., Meister, G., Bailey, S. W., Eplee, R. E., Jr., Feldman, G. C., Kwiatkowska, E., McClain, C. R., Patt, F. S., & Thomas, D. (2005). “The continuity of ocean color measurements from SeaWiFS to MODIS.” Proceedings of SPIE, 5882. doi: 10.1117/12.620069
• Morel, A., Huot, Y., Gentili, B., Werdell, P. J., Hooker, S. B., & Franz, B. A. (2007). “Examining the consistency of products derived from various ocean color sensors in open ocean (Case 1) waters in the perspective of a multi-sensor approach.” Remote Sensing of Environment, 111(1), 69–88. doi: 10.1016/j.rse.2007.03.012
• Barnes, B. B., Hu, C., Bailey, S. W., Pahlevan, N., & Franz, B. A. (2021). “Cross-calibration of MODIS and VIIRS long near infrared bands for ocean color science and applications.” Remote Sensing of Environment, 260, 112439. doi: 10.1016/j.rse.2021.112439
• Stramski, D., Joshi, I., & Reynolds, R. A. (2022). “Ocean color algorithms to estimate the concentration of particulate organic carbon in surface waters of the global ocean in support of a long-term data record from multiple satellite missions.” Remote Sensing of Environment, 269, 112776. doi: 10.1016/j.rse.2021.112776
• Lee, Z.-P., Du, K.-P., & Arnone, R. (2005). “A model for the diffuse attenuation coefficient of downwelling irradiance.” Journal of Geophysical Research: Oceans, 110(C2). doi: 10.1029/2004JC002275

NASA Technical Resources and Training

• NASA OBPG, R2022 Multi-mission Ocean Color Reprocessing.
• NASA ARSET: Monitoring Coastal and Estuarine Water Quality — Transitioning from MODIS to VIIRS
• NASA ARSET: Introduction to PACE Hyperspectral Observations for Water Quality Monitoring
• NASA CMR Search API documentation