The Aura spacecraft sits in a near-polar, sun-synchronous orbit with a period of about 100 minutes. The goal of the Aura spacecraft is to study chemistry and dynamics of the Earth's atmosphere with relation to ozone trends, changes in air quality and how various factors are linked to climate change. The spacecraft is designed for a 6-year lifetime. The LASP instrument, HIRDLS, has 8 primary objectives (taken from http://www.eos.ucar.edu/hirdls/)
1) To understand the fluxes of mass and chemical constituents (including greenhouse gases and aerosols) that affect the dynamics and composition of the troposphere, stratosphere, mesosphere, and thermosphere and link these regions together. These fluxes must be determined down to smaller scales than previously observed.
2) To understand the chemical processing, transport, and small-scale irreversible mixing of trace constituents in the middle atmosphere, including the chemical and dynamical processes responsible for creating the Antarctic (and perhaps Arctic) ozone holes.
3) To understand the momentum, energy, and potential vorticity balances of the middle atmosphere, by extending observations to smaller horizontal and vertical scales than has previously been possible. These small-scale processes are believed to be fundamentally important to the determination of some large-scale characteristics and are thought to cause irreversible chemical mixing.
4) To obtain climatologies of upper tropospheric, stratospheric, and mesospheric quantities, in particular, profiles of temperature, ozone, several radiatively active gases, aerosol, gravity wave activity, and cloud top heights. Seasonal, interannual, and long-term trends will be obtainable because of the five-year measurement sequence that will be provided by each EOS instrument, combined with pre-EOS measurements and future EOS observations.
5) To provide data to validate and improve numerical models of the atmosphere, in order to gain confidence in their ability to predict climate change. These simulations are critically dependent on the treatment of horizontal and vertical scales that are much finer than those currently observed.
6) To improve tropospheric temperature and water vapor profiles and cloud top height data that are used for climate and weather forecasting, by combining high vertical resolution limb data with data from operational nadir sounders such as AIRS and AMSU. This will yield valuable data from the tropopause region and the lower stratosphere, information that would not otherwise be available.
7) To improve the understanding of tropospheric chemistry through the use of temperature and constituent retrievals that extend into the upper troposphere, under favorable conditions. The combination of these observations with observations from other EOS instruments, and with chemical models, will yield information about the oxidation capacity of the atmosphere.
8) To improve the understanding of stratospheric and tropospheric aerosols and clouds by acquiring long-term high-resolution observations of their nature and distribution. Aerosols and polar stratospheric clouds are now known to play essential roles in the depletion of ozone in the lower stratosphere, and subvisible cirrus clouds in the upper troposphere significantly impact the radiative heating and cooling of the atmosphere.
