Frequently
Asked Questions About the ACRIMSAT Mission
What is an ACRIM anyway?
The Active Cavity Radiometer Irradiance Monitor (ACRIM) is a instrument designed
to fly in space and measure the total solar irradiance (the total light energy
from the sun). It is a radiometer because radiometers are instruments that
interact with light. It is an irradiance monitor because it measures light
for a long period of time. It monitors sun light. The words Active Cavity
describe the fact that the active cavity radiometer actively maintains the
temperature of its solar sensing cavity slightly hotter than the rest of
the instrument at all times using an automatic electronic servosystem. It
is Active.
What does ACRIM measure?
ACRIM measures the total energy of the light that comes from the sun.
Why do we make this measurement?
If we know the total amount of energy that the sun delivers to the earth, then
we can build scientific models of the earth's climate system. The energy
from the sun is the key energy input into this system.
What does the ACRIM data look like?
This
chart shows the daily average of total solar irradiance (TSI)
for the ACRIM I and ACRIM II experiments. ACRIM I flew on the
Solar Maximum Mission (SMM) spacecraft from 1980 to 1989. ACRIM
II flew on the Upper Atmosphere Research Satellite (UARS) from
1991 to the present. Each point on the curve is the daily average
of the total solar irradiance measurements taken by ACRIM on
the given day. The vertical axis is shown in watts per meter
squared (the amount of energy that hits a given surface at a
certain time). The horizontal axis is time shown in days.