- Objective:
- Demonstrate global ionospheric tomography and utilize the
technique to study ionospheric/thermospheric processes.
- Overview:
- Originally scheduled to be launched
in 1997 from
Vandenberg Air Force Base in
southern California, TERRIERS is designed to conduct a global
upper-atmospheric study. Using a combination of ground based and
space instruments, the satellite will survey
the upper atmosphere using a technique called tomography, measuring
ultraviolet light emissions, to construct an image of Earth's
ionosphere. Although the ionosphere has been studied in great detail
with various ground and spacebased instruments, currently there is no
means to obtain these types of global images. Such measurements are
crucial to the advancement of our understanding of many upper
atmosphere phenomena.
Due to delays in Orbital's Pegasus
launch queue
and NASA's desire to launch other, more expensive, missions, we are
currently scheduled to launch in April of 1999.
The TERRIERS project is a collaboration between the Center for Space Physics at Boston
University, AeroAstro , the
University of Illinois at Urbana-Champaign
(UIUC), the Naval Research Laboratory, MIT's Haystack Observatory,
Phillips Laboratory and
Cleveland Heights High School
- Mission Goals:
- TERRIERS' primary goal is to, for the first time, demonstrate
meridional 2-D (latitude-altitude)and global 3D imaging of the
ionospheric electron density and thermospheric photo-emission profiles
using EUV emissions and tomographic techniques
Secondary goals of TERRIERS focus on the study of several
ionospheric and thermospheric phenomena through the use of this novel
combination of techniques and observations.
As a tertiary goal, TERRIERS will test the utility of long term solar EUV irradiance
measurements using a new technique that we have recently proven on a sounding
rocket. GISSMO measures the solar EUV,
one of the primary sources for the upper atmosphere. Due to its day to day
variability, it is only possible to understand many atmospheric processes
with stable, long term measurements of the flux. GISSMO
was designed as a highly stable solar flux monitor which would operate over
long missions (one solar cycle or 11 years) without a significant change
in sensitivity. TERRIERS will provide the testing ground for satellite operation
of GISSMO and short term life testing.
- Science Background
- Studies of the Earth's upper atmosphere began to emerge as a
separate discipline during the early years of the twentieth
century. By the 1930's, Sydney Chapman put forward a theoretical
framework for the "electrically conducting layer" needed to account
for radio propagation experiments. These soon became the D, E and F
layers of the ionosphere -- stacked as it were one upon the
other. These were generalized subsequently into the concept of
spheres (as in the stratosphere, mesosphere, thermosphere,
magnetosphere, etc.), a more globally accurate picture than
plane-stratified-layers, but yet quaintly reminiscent of ancient
geocentric cosmologies of spheres within spheres. Today,as the century
draws to a close, the atmospheric science community has achieved a far
better level of understanding of the upper atmosphere as it strives to
understand it as moree than a series of concentric layers or
spheres. Current research work rests upon the appreciation that
atmospheric regions are not independent domains, but rather intermixed
(as is ionosphere and thermosphere) and mutually coupled
regions. While this coupling is easiest to describe in schematics of
vertical structure, spatial structure exists within a given region,or
in coupling processes that occur in latitude and longitude, as well as
from above and below. The non-spherical geometry of the terrestrial
magnetic field orders many aspects of coupling and structure.
