ABOUT CLOUDSAT

Part of NASA’s fleet of weather- and climate-tracking satellites, CloudSat uses advanced radar to examine the inner structure of clouds, helping researchers better understand how severe tropical cyclones as well as climate changes related to clouds occur.

In August 2010, CloudSat embarked on a new mission phase to study the genesis and patterns of tropical cyclones. Since its launch in 2006, CloudSat has played an instrumental role in new techniques for estimating the intensity of hurricanes from space, in addition to producing data about links between pollution and rainfall.

CloudSat was selected as a NASA Earth System Science Pathfinder satellite mission in 1999 to provide observations necessary to advance our understanding of cloud abundance, distribution, structure, and radiative properties. Since 2006, CloudSat has flown the first satellite-based millimeter-wavelength cloud radar—a radar that is more than 1000 times more sensitive than existing weather radars. Unlike ground-based weather radars that use centimeter wavelengths to detect raindrop-sized particles, CloudSat’s radar allows us to detect the much smaller particles of liquid water and ice that constitute the large cloud masses that make our weather.

Fun Fact: Planned as a 22-month mission, CloudSat has crushed its mission goals and is still collecting data a decade after launch. As the second of NASA’s Earth System Science Pathfinder missions, CloudSat has lasted two decades past its original concept developed in the 1990s!

INSTRUMENTS ONBOARD

The Cloud Profiling Radar (CPR)

The Cloud Profiling Radar (CPR) is a 94-GHz nadir-looking radar which measures the power backscattered by clouds as a function of distance from the radar. The CPR was developed jointly by NASA/JPL and the Canadian Space Agency (CSA). The overall design of the CPR is simple, well understood, and has strong heritage from many cloud radars already in operation in ground-based and airborne applications.

The design of the CPR is driven by the science objectives. To achieve sufficient cloud detection sensitivity, a relatively low frequency (i.e. <94 GHz) radar would require an enormous antenna and high peak power. At frequencies much greater than 100 GHz, a large antenna and high peak power are also needed due to rapid signal attenuation through cloud absorption. Furthermore, technologies at such high frequencies are less well developed. The 94-GHz frequency chosen by CPR offers the best compromise, meeting performance within the spacecraft resources. In fact, most existing airborne cloud radars operate at 94 GHz. These airborne radars provide extensive heritage for CPR on instrument design and technology, data processing, and retrieval algorithms. A primary frequency allocation of 94 GHz for spaceborne cloud radar sensing has been formally approved at the 1997 World Radio Conference.

OUTCOMES

- CloudSat has revealed how often the clouds above Earth rain and snow. This is information that we did not know before, principally because many regions on Earth are not instrumented on the ground to obtain this information, such as over the oceans and over sparsely-populated land areas such as the polar regions.

- It has revealed how much ice and water are contained in clouds globally.

- It has determined how clouds heat or cool the atmosphere.

- allowed scientists to understand how often and how quickly rain develops in clouds.

- provided the first quantitative estimate of global snowfall.

- Has given scientists a deeper understanding of how pollution, volcanic emissions and other atmospheric ‘aerosols’ interact with clouds to affect precipitation and cloud lifetime.

- provided unique insight into the effect of cloudiness on the acceleration of polar and Greenland ice melting.