$LastChangedDate: 27-Juil-2011 $

# CL_gm_equatorialSwath

Sensor view angle for an overlap ratio of 1 at equator

## Calling Sequence

       [view_angle]=CL_gm_equatorialSwath(alt,inc,[er,rotr_pla])

## Description

- Computes the view angle as seen from the satellite (angle from the descending vertical) so that the overlap ratio at equator is 1.

  The overlap ratio is the ratio Q=Leq/Ded where:

  - Leq: portion of the equator seen by the sensor during the time it crosses the equator.

  - Deq: gap between 2 consecutive ground tracks at equator.

- Notes:

  - The planet is assumed spherical, and the orbit circular.

  - The sensor is conic and oriented towards the descending vertical.

  - The gap between 2 consecutive ground tracks is computed taking the effect of J2 into account.

  - The result is undefined (%nan) if inclination is 0 or %pi.

## Parameters

alt:

  Satellite's altitude [m] (1xN)

inc:

  Orbit's inclination [rad] (1xN)

view_angle:

  Sensor half view angle [rad] (1xN)

er:

  (optional) Equatorial radius [m] (default is %CL_eqRad)

rotr_pla_sun :

  (optional) Mean apparent rotation rate of the Sun around the planet (default is %CL_rotrEarthSun)

## Authors

- CNES - DCT/SB

## Bibliography

- 1) Satellites orbites et missions - Michel Capderou

## See also

- CL_gm_equatorialOverlap

## Examples

    alt = [822.e3 630.e3] ;
    inc = [CL_deg2rad(98.72) CL_deg2rad(96.72)];
    [view_angle] = CL_gm_equatorialSwath(alt,inc)