Vaisala MITRAS BROCHURE

MITRAS Transmissometer

Reliable RVR with
MITRAS Transmissometer

Accurate RVR measurement reduces airport down­time and improves safety and reliability of
operations.
The MITRAS Transmissometer system provides You
with correct visibility data without breaks.

Vaisala’s MITRAS is a well­proven solution to Runway
Visual Range assessment. The
system has been in operational
use since 1986 and has demons­trated excellent performance in
international intercomparisons.
MITRAS provides many operat­ional and reliability benefits:

• Conformance to all ICAO and
WMO requirements for RVR and
Meteorological Optical Range
(MOR)

• Fully automatic operation with
excellent accuracy and stability

• Unique contamination detect­ion and compensation

• Double baseline for CAT IIIB
by means of two different beams
from one transmitter

• Extensive built-in monitoring
to verify performance and to
generate warnings before
failures actually occur

• Verified operation in all
weather conditions

SYSTEM STRUCTURE

The standard MITRAS Trans­missometer consists of a light
transmitter and a light receiver
installed at a suitable distance
from each other. MITRAS meas­ures transmission of white light
over the baseline path and con­verts the measurement value to
the corresponding MOR value.
The transmittance measurement
resolution of MITRAS is better
than 0.1 % and the measurement
accuracy is better than 1 %.

A single baseline MITRAS can be
easily and economically up­graded to a double baseline
system when extended measure­ment range is needed for CAT
IIIB applications. The two base­lines are realized by adding an
individual lens system in the
transmitter unit and a second
receiver unit. Excellent accuracy
is guaranteed because the two
separate light beams from the
single transmitter unit do not
interfere with each other.

Vaisala’s LM11 Background
Luminance Meter can be con­nected to a MITRAS transmitter
unit. The luminance sensor is
interfaced to the MITRAS pro­cessor unit and it shares the
same communication line with
the transmissometer.

MITRAS communicates the
measurement results to a host
system via a modem line. RVR
calculations are carried out by a
dedicated RVR computer or an
integrated airport weather
observation system and the
results are sent to various
displays.

COST SAVINGS THROUGH
EASY MAINTENANCE

Contamination of the optical
windows with time is inevitable
and it can have a significant
impact on RVR accuracy. MIT­RAS measures the window con­tamination and automatically
compensates for the loss in
measured transmittance. When

The visibility measurement ranges achieved
by single and double baseline MITRAS
systems are shown below. The baseline of
MITRAS can be freely selected between
10 ... 200 m.

Baseline MOR range RVR range*)

35 m 25 ... 1500 m 100 ... 1500 m
50 m 40 ... 2000 m 150 ... 2000 m
75 m 50 ... 3000 m 200 ... 3000 m
100 m 70 ... 5000 m 300 ... 5000 m
200 m 150 ... 10 000 m 500 ... 10 000 m

*) The actual RVR range is dependent on runway lighting.
The values shown are based on usual lighting arrangements.

Baseline MOR range RVR range*)

10 and 75 m 7 ... 3000 m 40 ... 3000 m
10 and 200 m 7 ... 10 000 m 40 ... 10 000 m

(Double baseline is required in CAT IIIB operating category.)