The effect of the Atmosphere on the Satellite

The effect of the Atmosphere on the Satellite

1. ATMOSPHERIC DRAG

2. •Atmospheric drag is a frictional force caused by
the atoms and ions of the atmosphere opposite
to the velocity of the satellite.
•Atmospheric drag lowers and affects the low
satellite orbits mostly.
•It takes away energy from the orbit of the
satellite i.e it reduces the ellipticity of the orbit,
making it more and more circular and causing a
loss of altitude of a circular orbit.

3. PERTURBATIONS
Atmospheric Drag
Perigee remains same, Apogee decreases

4. •Atmospheric drag decreases the
eccentricity and semi major axis of
the orbit due to loss of energy.
•At very low altitudes the friction cause
excessive heat on the satellite
resulting in the burning of the satellite.

5. •As the eccentricity of the orbit
decreases it gets more and more
circular and when orbit gets circular its
semi major axis also reduces.
•As the altitude of the circular orbit
decreases its velocity will increase more
and more as satellite gets nearer to
earth.

6. •In elliptical orbits altitude at apogee
decreases and perigee remains constant.
It decreases the orbit and becomes more
circular from elliptical.
•Atmospheric drag reduces the life of the
satellite.
•Higher the drag lower the satellite life.

7. For example satellite life at an altitude of
400 kms will be of few months while the
satellite life at about 800 kms will be of
few years. At low altitudes friction causes
lot of heat on satellite which finally burns
the satellite.

8. •A satellite, orbiting around the Earth,
would continue to orbit forever if gravity
were the only force acting on it.
•However, satellites below 2000 kilometers,
are actually travelling through the Earth's
atmosphere.

9. •Collisions with air particles, even at these high
altitudes, slowly act to circularize the orbit and
slow down the spacecraft causing it to drop to
lower altitudes.
•Russian launched their first satellite SPUTNIK-1
in 1957 in LEO.
•Due to drag forces its orbit gradually changed
from the upper atmosphere which decreased its
orbit.

10. •While tracking the decay of the satellite
path scientists observed that the density of
the upper atmosphere was much more
than estimated and expected, which made
the satellite to loose its orbit and finally
SPUTNIK-1 finished in the atmosphere on
January 4, 1958

11. •The drag force on the satellite is given as:
2
2
1
VCDAF
D 

12. •F
D =drag force
•C
D =drag coefficient
•A =area of cross section of the
satellite
•ℓ =atmospheric density
•v =satellite velocity

13. m
F
a
D

m
VAC
a
D
2
2



14. DEPENDENCE FACTORS
•Atmospheric drag depends upon the
•ATMOSPHERIC DENSITY
•Higher the density, more the drag
(D=M/V)
•i.e more the density, more the mass and
more the drag.

15. ALTITUDE
•Lower the altitude, higher the drag
VARIABLE SOLAR DISTANCE
•Closer the satellite to the sun more will
be the drag

16. SOLAR WIND
•High-speed charged
particles constantly
blowing off the Sun.
•The solar wind has a
significant influence
on our ionosphere,
the Earth's magnetic
field, and on
telecommunication
systems.

17. SOLAR WIND
The solar wind
contains roughly
equal number of
electrons and
protons, along with
a few heavier ions,
and blows
continuously from
the surface of the
Sun at an average
velocity of about
400 km/second.

18. •SATELLITE FRONTAL AREA
•More the satellite area exposed, more
will be the drag e.g drag in case of 3-axis
stabilized satellite is more effective than
spin stabilized satellite.

19. •Solar wind causes radiation pressure on
the satellite
•Effects similar to atmospheric drag
•Effects are more pronounced on
satellites with large surface areas

20. HOW IS SPACE WEATHER
INVOLVED
•The density of the air particles responds
sensitively to the solar activity, season,
longitude, latitude and local time.
•Emissions from the Sun (including, the
highly variable Xray and ultraviolet output)
cause the upper atmosphere to heat and
expand.

21. These energetic solar outputs increase
dramatically during periods of high solar activity
and hence causes the heating and expansion of
the atmosphere in these regions.

22. PERTURBATIONS
Electro-Magnetic
•Interaction between the Earth’s magnetic
field and the satellite’s electro-magnetic
field results in magnetic drag

23. Latitude & Longitude Effect
•We know that earth is non-spherical as it
has a bulge along the equator which
means that its equatorial radius is more
than the polar radius.
•Wind thickness is more at regions that are
at equator and at low latitudes than at
poles or at higher latitudes .

24. Effect of Seasons
•In case of higher solar angles sun is more
intense.
•It rises high up in the atmosphere, heats
the atmosphere more and results in more
expansion of the atmosphere.
•This high expansion effects the satellite
more.

25. Solstices and Equinoxes at 40°N

29. •This creates added
drag in the area
where satellites and
the Space Shuttle
orbit. This drag
could slowly pull
such spacecraft out
of orbit earlier than
expected.