Researchers at The Johns Hopkins University Applied Physics Laboratory (APL) are proposing a new space-based monitoring system that would help scientists answer some of the most fundamental questions surrounding Earth's changing climate.

Earth's Radiation Imbalance System, or ERIS, would provide the most detailed data ever about differences in the amount of radiant energy entering and leaving the Earth, one of the keys to unveiling the real reasons behind observed climate change.

The program expands on the success of a current Earth science mission - the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) - that, like ERIS, partners APL with global satellite constellation operator Iridium Communications Inc. APL's Brian Anderson is principal investigator (PI) of AMPERE.

"AMPERE showed us how well a public/private partnership between the scientific community, industry and a government sponsor could work," says Lars Dyrud, senior scientist at APL and PI for ERIS. "Our ERIS team proposes to answer even more critical questions about our planet."

ERIS would consist of small radiometers, each roughly the size of a red clay brick, integrated into each of the 66 satellites within Iridium's NEXT constellation, the company's next-generation network that is under development and scheduled for initial deployment in 2015. Developed as a NASA Earth Venture-2 mission proposal, ERIS would operate as a hosted payload aboard the Iridium NEXT satellites.

Piggybacking scientific instruments like ERIS onto commercial satellites can provide immense cost savings. ERIS would utilize the Iridium NEXT satellites as the largest single satellite constellation available for a NASA science mission ever - at a fraction of historic mission costs for a single satellite.

"ERIS presents a once-in-a-lifetime chance to measure the Earth's radiation imbalance everywhere, all the time," says Dyrud. "The science objectives that ERIS proposes will be pivotal to truly understanding global climate change."

Climate change studies have, for decades, relied on incomplete and sporadic data to create climate models; ERIS would provide, for the first time, a set of detailed, nearly-constant global data about energy changes on Earth. ERIS will also let researchers explore for the first time how clouds, hurricanes and volcanoes affect outgoing radiant energy in near real-time.

Another strength of the ERIS proposal is its experienced team: APL's Cindy K. Kim serves as project manager; Iridium is represented by Om Gupta, director of business development for Iridium NEXT; and the science lead and deputy PI is Warren J. Wiscombe, senior scientist, NASA Goddard Space Flight Center and former chief scientist of the Department of Energy's Atmospheric Radiation Measurement (ARM) program. Steven R. Lorentz of L-1 Standards and Technology serves as deputy PI, and the Charles Stark Draper Laboratory would build the ERIS instruments.

A core science team has been assembled, with researchers representing NASA, National Center for Atmospheric Research (NCAR), Brookhaven National Laboratory and universities across the U.S. and Canada.

Inspiration for ERIS came in part from the success of AMPERE, a 2010 research project involving APL and Iridium's current 66-satellite network. AMPERE uses existing devices on the satellites to generate real-time magnetic field measurements as part of a new observation network to forecast weather in space.

"ERIS is an excellent example of how hosted payloads on the Iridium NEXT constellation can benefit scientific research," Iridium's Gupta says. "The real-time transmission, global coverage and low cost of hosted payloads on Iridium NEXT make it ideal for doing planetary scientific research. Our strong partnership with APL on AMPERE mapped a successful path for ERIS."

APL, together with its partners, provides combined expertise in magnetometers, small-run high tech manufacturing, space instrument design, mission planning, execution experience and Earth science research.

"ERIS is the latest example of the innovative solutions that our staff consistently develop for our sponsors," says John Sommerer, head of the APL Space Department.

"We look forward to evolving the successful collaboration on AMPERE, and to providing NASA with a global, near real-time solar radiation monitoring system, leveraging Iridium's commercial launches to escape the launch vehicle 'cost-squeeze' challenging all NASA science missions."