Polarized Submillimeter Ice Cloud Radiometer (PolSIR)

Overview

The Polarized Submillimeter Ice-Cloud Radiometer (PolSIR) is a new NASA satellite mission. Its goal is to understand the influence of ice clouds on our climate. Ice clouds have been identified by the Intergovernmental Panel on Climate Change (IPCC) as one of the biggest unknowns in our understanding of the climate system and how it changes.

PolSIR consist of two satellites that will be launched in 2027 and will run until approximately 2030. They will circle the earth around the tropics and sub-tropics and observe ice clouds and their diurnal variability. These observations will improve climate models and will ultimately lead to better predictions of how our climate will be changing over the next thirty to fifty years, thereby helping decision makers adapt to climate change.

PolSIR is led by Ralf Bennartz, principal investigator at Vanderbilt University in Nashville, Tennessee, and by Dong Wu, deputy principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. This is the first ever satellite mission led by Vanderbilt University.

Mission and Science objectives

In May 2023, NASA selected PolSIR as the latest addition to its Earth Venture Instrument (EVI-6 cost capped) class missions with an investment of $42M not including launch. PolSIR addresses key research priorities related to uncertainties in our current understanding in high clouds and cloud feedbacks as formulated in NASA’s latest Decadal Survey and in the latest Intergovernmental Panel on Climate Change (IPCC) Assessment. In this context, PolSIR will address the following objectives:

Science Objective 1:
Constrain diurnal cycle amplitude, form, and timing of the ice water path (IWP) in tropical and sub-tropical ice clouds
Science Objective 2:
Determine the diurnal variability of ice clouds in the convective outflow areas and understand relation to deep convection.
Science Objective 3:
Determine the relationship between shortwave and longwave radiative fluxes and the diurnal variability of ice clouds
Application Objective 1:
Enable improvement of climate models by providing novel observations of the diurnal cycle of ice clouds

Satellites and Instruments

The PolSIR mission consists of two 12U CubeSats, each equipped with a six channel, cross-track scanning polarized submillimeter radiometer in the spectral range of 325–680 GHz. The two PolSIR satellites fly in separate, 51-degree inclination, non-sun-synchronous orbits, taking science measurements between ±35 degrees latitude enabling monthly sampling of the diurnal cycle of ice clouds and their microphysical properties in the tropics and sub-tropics. PolSIR’s observation concept provides significant benefits over the Program of Record (PoR) as well as synergies with future missions which will either be in sun-synchronous orbits, thus not sampling the diurnal cycle, or lack the observation frequencies needed to fully observe ice water path (IWP).

Footprint size <15km at nadir
Radiometric accuracy NEDT <2K

Science Team

The mission is led by Ralf Bennartz, principal investigator at Vanderbilt University in Nashville, Tennessee, and by Dong Wu, deputy principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. NASA Goddard will provide the project management team that builds the two instruments, while science operations will be conducted by the Space Science and Engineering Center at the University of Wisconsin - Madison. The two spacecraft will be built by Blue Canyon Technologies in Lafayette, Colorado. Launch of the two satellites is currently anticipated for late 2027.

Project Team Members

Bennartz	Ralf	Vanderbilt
Wu	Dong	NASA-GSFC
Adams	Ian	NASA-GSFC
Barahona	Donifan	NASA-GSFC
Berndt	Emily	NASA-MSFC
Brogniez	Helene	U Paris Saclay
Braun	Jessica	UW-Madison
Ehsan	Negar	NASA-GSFC
Elsaesser	Greg	GISS/Columbia U
Gong	Jie	NASA-GSFC
Johnson	Ben	UCAR
Karpowicz	Bryan	NASA GMAO
Kroodsma	Rachael	NASA-GSFC
Loveless	Daniel	Indiana University
Merrelli	Aronne	U-Michigan
Pettersen	Claire	U-Michigan
Racette	Paul	NASA-GSFC
Rapp	Anita D.	Texas A&M
Vanags	Chris	Vanderbilt

News

NASA:

NASA Mission to Study Ice Clouds, Help Observe Our Dynamic Atmosphere
Vanderbilt:

Vanderbilt University’s Ralf Bennartz to lead NASA mission to study ice clouds
NASA:

PolSIR: Polarized Submillimeter Ice Cloud Radiometer
U-Michigan:

PolSIR: Pettersen, Merrelli Join NASA Mission to Study Ice Clouds
Texas A&M:

Atmospheric Sciences Professor On Team Selected For New NASA Satellite Mission