OMPS measures the global distribution of the total atmospheric ozone column on a daily basis. It also measures the vertical distribution of ozone from about 15 km to 60 km, though somewhat less frequently. Ozone is an important molecule in the atmosphere because it partially blocks harmful ultra-violet light from the sun. The Nadir instrument looks directly below the satellite while the Limb instrument looks at an angle to the Earth's surface. Combining the two views will enhance the ability of scientists to measure the vertical structure of ozone, which is important in understanding the chemistry of how ozone interacts with other gases in the atmosphere. The third portion of the suite is the Main Electronics Box (MEB), which controls the operation of the instruments and then captures and routes the data to the spacecraft. The NPP OMPS instrument contains both the Nadir and Limb sensor while JPSS-1 is flying only the Nadir sensor.
OMPS carries on a long tradition of space borne measurements of ozone beginning in 1970 with the Nimbus 4 satellite and continuing with the Solar Backscatter Ultraviolet (SBUV and SBUV/2) and Total Ozone Mapping Spectrometer (TOMS) instruments on various NASA, NOAA, and international satellites. Over the more than 30 year period in which these instruments have been operating, they have provided a very detailed and important long-term record of the global distribution of ozone.
The instruments measure ozone by collecting light from the sun that has been reflected off of the atmosphere. Ozone molecules absorb some of this light and these absorption features are used to calculate the amount of ozone present over the entire globe.
OMPS, the Ozone Mapping Profiler Suite, will continue the US program for monitoring the Earth's ozone layer using advanced hyperspectral instruments that measure sunlight in the ultraviolet and visible backscattered from the Earth's atmosphere. OMPS will launch as part of the JPSS mission, with the first instruments flying on NPP. OMPS is a three-part instrument: a nadir mapper that will map global ozone with about 50-km ground-resolution, a nadir profiler that will measure the vertical distribution of ozone in the stratosphere, and a limb profiler that will measure ozone in the lower stratosphere and troposphere with high vertical resolution.
OMPS is designed to answer the scientific question: is the ozone layer recovering as expected? After the sharp decrease in ozone observed in the 1980s, and the development of an ozone hole over Antarctica each spring linked to the release of chlorofluorocarbons (CFCs), NOAA and NASA were given the responsibility of monitoring Earth's ozone layer. NOAA has flown a series of SBUV/2 ozone profiler instruments, while NASA has flown a series of TOMS instruments that map global ozone. OMPS will continue these measurements.
The nadir mapper instrument on OMPS will provide daily maps of total column ozone on a global basis. This is important for monitoring the development and breakup of the Antarctic ozone hole each year and for watching in detail the changes in the spatial distribution of ozone. In order to understand the cause of the observed ozone changes, it is important to distinguish the altitude at which the change is occurring. Since ozone in the upper stratosphere is controlled mostly by gas phase chemistry, this is the place to look for signs of ozone recovery.
As the CFCs released in past decades slowly decrease, instruments should detect ozone levels near 40 km recovering to 1980 levels. The OMPS nadir profiler instrument, which is capable of accurate long-term measurements of ozone in the upper stratosphere, will watch for signs of ozone recovery. Ozone changes in the lower stratosphere and troposphere will be complicated by the effects of global warming. The limb profiler will make high-resolution measurements of ozone in the lower stratosphere and troposphere to help distinguish ozone change from climate change.
While ozone measurement is the primary purpose of OMPS, it is also capable of providing global mapping of other atmospheric constituents, including aerosols and SO2. OMI, the Dutch-built Ozone Mapping Instrument flying on the Aura spacecraft, is currently measuring SO2 and ash from volcanic eruptions. When ash from the Eyjafjallajokull volcano in Iceland shut down aviation in Europe for a week in the spring of 2010, space-based measurements of the volcanic cloud from the OMI Ozone Mapping provided aircraft safety warnings. (See figure at right.) OMPS will have a similar ability to measure SO2 and ash.
Similarly, dust clouds blowing off the Sahara and smoke from fires in can be tracked by the ozone mapping instrument. Every year, extensive fires in Africa and South America are used to clear land, leading to extensive smoke clouds that spread through the tropics. Large forest fires in North America and Siberia also produce large smoke clouds. OMPS will have the capability to track these smoke clouds.