The spatial resolution of a real aperture BIPAR system is defined by the beam- 
width of the scanning pencil beam antenna (see fig. 3). The nominal value of 
the spatial resolution in azimuth ó, (flight direction) and elevation 6p (per- 
pendicular to flight direction) is defined at a scan angle of 0 degrees. 
ÔA/E = ne (for Nadir) (6) 
When the pencil beam is pointed to a outermost edge of the swath the spatial 
resolution is degraded to 
D max = La cos (P-72) (7) 
à zc I. (8) 
max LE cos (05/2) 
where L, and Lg are the effective antenna dimensions in azimuth and elevation, 
ps is tie maximum scan angle between left and right edge of the swath and n is 
an integer value being n=2 for mechanical and n=3 for electronical scanning of 
the pencil beam. This difference considers a broadening of the antenna eleva- 
tion beam toward the swath edges in case of electronical scanning. 
The width of the BIPAR swath W is given by 
A 
W=H [2tan(p_/2) + ——— mmm (9) 
nies Lg colo 0 
and the available pixel integration time Ti is defined by 
Ô 
T. = (10) 
1 VA Np Nr 
[th iN s (OE 0 "e 
where v, is the aircraft velocity, N, is the number of independent looks 
required for improvement of the radiometric resolution, and ©. is the antenna 
elevation beamwidth. The theoretical integration gain is defined by the time- 
bandwidth product Ty*B;- 
3.3 Radiometric System Performance 
  
Applying the time-bandwidth product and the integration efficiency n, equa- 
tion 6 can be written as follows: 
— 
— 
sr 
3 
ni 
Pp PAL oc, Zi 5. TT (11) 
where S is the received signal power and B, is the system bandwidth assuming a 
matched receiver chain. 
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