The NPP mission is the bridge between the nation’s Earth Observing System (EOS) satellites and the next generation Joint Polar Satellite System (JPSS). NPP will help scientists understand, monitor and predict long-term climate behavior and also provide vital near-term weather data to meteorologists. The mission hosts a suite of advanced-technology remote sensing instruments that will provide critical data for the nation.
Polar-orbit satellites contribute vital information for national forecasts, severe weather warnings, search and rescue operations, military contingency planning and climate monitoring. The nation’s ability to understand its climate and weather is central to our economic competiveness and the safety and security of its citizens. NPP will help NASA continue its long record of climate monitoring established by EOS. This data record provides critical information about clouds, oceans, vegetation, ice and the atmosphere.
The Role Of NPP
NPP has a unique role in that it will monitor the health of the Earth from space. This will be the first satellite to acquire a wide range of land, ocean and atmospheric measurements while also preparing to address the nation’s requirement for operational weather forecasting.
Ball Aerospace is responsible for designing and building NPP satellite bus, the Ozone Mapping and Profiler Suite (OMPS) instrument, integrating all instruments, and performing satellite-level testing and launch support.
NPP has a projected lifespan of five years and will attain a sun-synchronous orbit, with 16 orbits per day at an altitude of 512 miles (824km), producing coverage of nearly the entire Earth. The spacecraft bus is the Ball Configurable Platform (BCP 2000) and NPP’s dimensions are 4.028m x 2.610m x 2.206m with a weight of 4,600 pounds (2,100 kilograms).
The Launch
NPP is scheduled to launch in October 25, 2011 from Vandenberg Air Force Base in California via a United Launch Alliance Delta II launch vehiclee.
The satellite will carry five instruments, all of which can trace their heritage to instruments on NASA’s Terra, Aqua and Aura missions, on NOAA’s Polar Operational Environmental Satellite spacecraft, and on the DoD’s Defense Meteorological Satellite Program.
– The Visible/Infrared Imager Radiometer Suite (VIIRS)
– The Cross-track Infrared Sounder (CrIS)
– The Advanced Technology Microwave Sounder (ATMS)
– The Ozone Mapping and Profiler Suite (OMPS)
– The Clouds and the Earth Radiant Energy System (CERES)
As presented at NASA’s NPP Missions infosite, Jennifer LaPan of NASA’s Langley Research Center offered the following excerpted information regarding the purpose of the NPP satellite, as well as an interview of Norman Loeb, the CERES instrument’s principal investigator.
CERES is an acronym for Clouds and Earth’s Radiant Energy System. Measuring climate is not as easy as popping a thermometer into Earth’s mouth every day. The crux of climate change is energy. In 1984, NASA began measuring and keeping a record of changes in Earth’s energy with a satellite instrument known as ERBE (Earth Radiation Budget Experiment) and then its successor, CERES (Clouds and Earth’s Radiant Energy System).
Five satellites and 27 years later, not a single year has passed without a record of Earth’s energy budget. This year, the climate-monitoring torch is being passed to the NPOESS Preparatory Project (NPP), a satellite carrying the fifth edition of CERES.
Jennifer LaPan
Why are we measuring energy on Earth? What does that have to do with the Earth getting warmer?
Norman Loeb
Just like you have a budget at home that you must balance with income coming in and expenses going out, the climate has a very similar process. Sunlight is the incoming resource (or energy), and the outgoing energy back to space is from reflected sunlight and emitted thermal radiation. The balance of incoming and outgoing energy is commonly referred to as the Earth’s energy budget. A balanced energy budget keeps Earth’s temperature at a consistent level. However, we currently have less energy leaving the Earth than is necessary to keep a steady temperature. Most of the extra, trapped energy is stored in the ocean, contributing to sea-level rise, and the remainder melts snow and ice over land and warms the atmosphere.
Jennifer LaPan
Can you point to the cause of this trapped energy?
Norman Loeb
We feel confident that one reason for the change in Earth’s energy budget is due to greenhouse gases. Greenhouse gases, like water vapor and carbon dioxide (CO2), block energy from radiating back out to space. Just as if you were to put another blanket on your bed at night, a layer of greenhouse gases makes the Earth warmer by not allowing heat to fully escape. The more CO2 we put in the atmosphere, the thicker the blanket we have, and the warmer the Earth gets.
A second key component of climate change is the role of clouds. The CERES team combines measurements made by other instruments on the same spacecraft as the CERES instrument to observe changes in cloud properties in conjunction with changes in Earth’s energy budget. The influence of clouds on the energy budget is complex because clouds both reflect sunlight back to space and block energy from radiating to space. Which of these two dominates depends upon the properties of clouds, such as their amount, thickness and height. As the Earth undergoes changes in its climate, cloud properties may change in ways that may amplify or offset climate change. Understanding the influence of clouds on the energy budget is therefore a critical climate problem.
Based on all of the ERBE and CERES energy data that has been collected, how much, exactly, has the energy budget changed in the last few decades?
Norman Loeb
We measure the energy coming into earth in watts per square meter. Averaged over the entire planet, the sun gives us about 340 watts per meter (about the energy radiated from six incandescent light bulbs) yearly. The Earth returns an equal amount of energy back to space, keeping the temperature constant. However, because greenhouse gases are preventing some energy from leaving, there appears to be a little over 0.8 watts per square meter that aren’t leaving. This trapping process doesn’t change the atmospheric temperature immediately, because most of this excess energy is absorbed and stored in the ocean. However, over the past century the global temperature has risen 1.44 degrees Fahrenheit (0.8 degrees Celsius).
Jennifer LaPan
There are still CERES instruments actively taking measurements of Earth’s energy budget from space. Why do we need another CERES instrument on NPP?
Norman Loeb
The CERES instruments on the Aqua and Terra satellites are indeed continuing to take measurements, however, both of these instruments have exceeded their expected lifetime. While we are happy they have continued to provide data, they could stop working at any time.
The easiest way to see significant changes in Earth’s climate is to know what the Norman pattern of incoming and outgoing energy looks like and to keep a continuous record. We’ve been tracking those patterns with CERES, but if we were to lose an instrument before another was launched, we would lose the ability to intercalibrate the newer instrument with the older one, and would also lose time interval of data. It would be exceedingly difficult, if not impossible, to accurately tie the two records together, and it would be impossible to accurately determine what happened to the energy budget during the measurement gap. We can’t just guess the missing measurements and pencil them in, nor can we correct for any calibration differences between the two instruments without having overlap; we essentially have to reset the climate record to zero and the separate pieces of the record are forced to stand on their own.
A long data record also helps us sort out uncertainties that we still have with climate change. One of the biggest mysteries in predicting climate change is the impact of clouds on the energy flow through the Earth, and having CERES on NPP will allow us to continue to study this relationship.