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Task 2. Read and translate the text.

Text 2 Main techniques of satellite geodesy

Main techniques of satellite geodesy are:
1. Earth to Space methods (A satellite may be observed with
ground-based instruments).
2. Space to Earth methods (A satellite may carry an instrument or

sensor as part of its payload to observe the Earth)
3. Space to Space methods (A satellite may or use its instruments
to track or be tracked by another satellite)

Earth-bound methods

Earth-bound methods are the most advanced, because the
observation process is better under control. With the exception of
radar altimetry, the methods mentioned in (2) and (3) are still under
development or in their initial operational phase.

In satellite laser ranging (SLR) a global network of observation
stations measure the round trip time of flight of ultrashort pulses of
light to satellites equipped with retroreflectors. This provides

instantaneous range measurements of millimeter level precision which
can be accumulated to provide accurate orbit parameters, gravity field
parameters (from the orbit perturbations), Earth rotation parameters,
tidal Earth's deformations, coordinates and velocities of SLR stations,

and other substantial geodetic data. Satellite laser ranging is a proven
geodetic technique with significant potential for important
contributions to scientific studies of the Earth/Atmosphere/Oceans

system. It is the most accurate technique currently available to
determine the geocentric position of an Earth satellite, allowing for the
precise calibration of radar altimeters and separation of long-term

instrumentation drift from secular changes in ocean surface
topography. Satellite laser ranging contributes to the definition of the
international terrestrial reference frames by providing the information

about the scale and the origin of the reference frame, the so-called
geocenter coordinates. Example:LAGEOS
Doppler positioning involves recording the Doppler shift of a
radio signal of stable frequency emitted from a satellite as the satellite

approaches and recedes from the observer. The observed frequency
depends on the radial velocity of the satellite relative to the observer,
which is constrained by orbital mechanics. If the observer knows the

orbit of the satellite, then the recording the Doppler profile determines
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