PACE Clouds Challenge

Challenge Dates: 15 September – 15 October 2026

NASA scientists working on the PACE satellite mission are asking for your help to collect Clouds observations when the PACE satellite is passing over your location. PACE Atmosphere lead, Dr. Andy Sayer, is interested in comparing your ground-based observations of clouds to PACE data to get a sense of how well PACE measures cloud edges and total cloud cover. Dr. Sayer is specifically looking for GLOBE Clouds observations taken within a 5-minute window of PACE passing overhead during the PACE Clouds Challenge, which will run from 15 September to 15 October 2026. 

Learn more about PACE and the challenge at an upcoming GO Connect webinar on 27 August at 12 pm ET (16:00). 

Register for the PACE Clouds Challenge 2026: Volunteer Training webinar on 9 September at 3:00 pm ET (19:00 UTC) or in Spanish on 11 September at 3:00 pm ET (19:00 UTC).

What Is PACE?

PACE, also known as the Plankton, Aerosol, Cloud, ocean Ecosystem satellite, provides a unique hyperspectral view of the entire planet every 1–2 days designed to reveal invisible information about tiny algae (fish food) in the sea, plants on the land, and particles in the air. 

PACE launched on 8 February 2024 and is now in the phase in which scientists are learning how to use the information it provides to study clouds and aerosols. PACE measures how clouds and aerosols (tiny particles in the atmosphere) absorb and reflect sunlight to provide information about cloud cover and cloud type — key factors in weather and visibility forecasts. This information can also provide insight into how aerosols and clouds interact and how aerosols and clouds affect climate - things that are not well understood.

How You Can Help

To help support PACE science, Dr. Sayer is asking for your Clouds observations — especially photos — taken as close to the time PACE is over your location as possible. Timing is critical! 

To collect data in the 5-minute optimal observation window:

  • Set the PACE overpass alert in the GLOBE Observer app.
  • Five minutes before the PACE overpass, be in position outside and start your Clouds observation.
    • NOTE: The timestamp on your data is the time you open the clouds tool in the app. To make sure the data collection time aligns with PACE, please DO NOT tap the Clouds button until you are outside and ready to collect data. 
  • Collect all six cloud photos. If you start the observation 5 minutes before the overpass, the photos will be taken during the optimal observation window. 
  • Please do not take Clouds observations at night.

Go Above and Beyond:

  • Tell us what type of phone or device you are using (e.g., iPhone 13 Pro, Samsung Galaxy S26) in the “Field Notes” section found right below the Feature Photos options. This information will help Dr. Sayer know how much of the sky is included in each photo. 
  • Submit multiple observations in one day if PACE is passing overhead more than once (daytime observations only please). 

It is possible you will be able to collect data up to twice a day during daylight hours, depending on PACE overpass timing in your area. 

From the Scientist

“We want to be able to identify whether or not each pixel in a satellite image is a cloud or not, because if it's cloudy we want to determine the properties of that cloud, and if it's not cloudy we want to determine the properties of the atmosphere and surface underneath the cloud. So cloud detection is normally the first step in a satellite data processing stream. However, it is difficult to know objectively how well the cloud detection techniques work, especially near cloud edges and in situations where clouds are broken (given our pixels are about 1.2 km across). So the ground observers will help us to assess that.”—Dr. Andy Sayer, NASA PACE Satellite

Thank You for Participating

If your observation falls in the PACE optimal observation window, you will be notified with a satellite match email for that observation. Volunteers who submit observations during the optimal observation window AND complete that observation with all six photos will receive a certificate of recognition.  Additional badges will be awarded to those who set a streak collecting daily PACE observations.

Resources

Just Getting Started?

Learn More About Cloud Types and Cover

  • Sky Window
    This resource allows you to cut out the rectangle in the middle of the Sky Window and use the information on the frame to help describe sky conditions and identify clouds.
  • GLOBE Cloud Cover and Estimation Interactive
    This interactive web-based tool allows you to calibrate your eye by practicing cloud cover estimation using images on the computer. 
  • Estimating Cloud Cover Activity
    In this activity, you create a cloud collage and ask your friends to guess the percentage of cloud cover (watch video demo). You only need paper (white and blue), scissors, glue or tape, and a marker or pencil for this activity. Expand or adapt this activity by printing photos of the sky and asking participants to identify the cloud coverage.