IAPRS & SIS, Vol.34, Part 7, “Resource and Environmental Monitoring”, Hyderabad, India,2002
MULTI FREQUENCY SCANNING MICROWAVE RADIOMETER (MSMR) SENSOR
PERFORMANCE
Shashikala Palsule, Anjali Garg, Hetal Pandya, Anuja Sharma
Data Quality Evaluation Division, SIIPA, Space Applications Center, ISRO, Ahmedabad-15, India
shashi@ipdpg.gov.in,anjali @ipdpg.gov.in,hetal @ipdpg.gov.in,anuja@ipdpg.gov.in -
KEYWORDS: Calibration, Antenna & Brightness Temperature Data, Geophysical Parameter, Geo-location, Grid Resolution,
Sensitivity
ABSTRACT:
The Multi frequency Scanning Microwave Radiometer (MSMR) is four frequencies (6.6 Ghz, 10.65 Ghz, 18.0 Ghz, 21.0 GHz), Dual
polarized (H & V) microwave Sensor. This microwave radiometer is flown on IRS-P4 satellite which was launched by PSLV on
26th May 1999 from ShriHari Kota (Shar), India. This radiometer measures the dual polarized microwave radiance from the earth
Ocean surface and atmosphere. It has the revisit capability of two days. This paper highlight MSMR sensor performance results
obtained by Data Quality Evaluation (DQE) system for data product generated routinely at Balanagar, Hyderabad. DQE system has
developed operational Software Package to monitor & quantify various parameters like Sensor Data Reception Quality, System
Calibration Performance, Stability of Antenna Scanning mechanism & Receiver Junction Temperature. Laboratory measured
Antenna Pattern as Half Power Beam Width, Beam Efficiency, Side lobes are also estimated. Radiometric performance on uniform
pre-defined targets (Ocean, Desert) is evaluated for Relative Channel Sensitivity Performance. Relative Global Geolocation
Performance evaluation procedure was adopted by selecting land-sea-land transition tips from Greenland, Australia, India & South
Africa. The. detailed statistical Performance analysis on RAW/ATD/BTD Product shows that receiver-engineering performance is
stable from Hot/Cold Calibration data and antenna-scanning stability is within 0.5%. Radiometric Performance is within 1°k. and
Geolocation of Product is within +/- 1.2 grid resolution.
1.0 INTRODUCTION
The Multi frequency Scanning Microwave Radiometer
(MSMR) onboard IRS-P4 satellite was launched on 26^ May
1999, Specifications of MSMR Payload are given in Table 1
Frequencies(GHz) 6.6,10.65,18.0,21 H&V Polarization
Angle of incidence 50°C
Swath 1360 Km
Scanning Conical Circular Scanning
Repetivity 2 Days
Scan Time Period 5.37 seconds
Angular Scan Speed | 11.16 RPM
Dynamic Range 10°k to 330°k
Temperature Ideg K
Sensitivity t
Frequency (GHz) 6.6 10.65 18.0
21.0
Beam Footprint | 105 66 40
(Km) Scan 34
Beam Footprint | 67 43 26
(Km) Pixel 22
Table 1 Sensor Specifications
Two point internal calibration approach has been utilized by
using dedicated horn antenna viewing the cold space (2?7k) and
a black body at a high temperature (receiver ambient
temperature) is used for the hot reference. The fore half period
of circular conical scan is utilized for data collection and the aft
period is effectively used for cold and hot calibration
sequences. Two sets of internal calibration data is acquired just
before and after data collection cycle. Analog & Digital
Telemetry subsystem (ADTMS) measures 51-junction
temperature precisely. The radiometric sensitivity of MSMR
system depends upon receiver pre-detection bandwidth,
Integration time, Type of receiver, Antenna and receiver
temperature, Gain measurement accuracy.
2.0 MSMR DATA PRODUCTS
The application of this payload is for estimation of
oceanographic / meteorological parameters. The 6.6 GHz to
10.65 GHz channels are used for estimating sea surface
temperature and wind speed. The 18.0 GHz and 21.0 GHz
channels are useful for estimating climatic and atmospheric
humidity measurement.
The MSMR data product gets generated routinely 24 hr data as
a unit product. Each product is starting from 00.00 hrs to
23.59.59.999hrs. This data product corresponds to Play Back
mode, which is operational mode of mission. Real Time data is
available for duration of 10 minutes & area coverage
corresponds to visibility of Shadnagar Earth Station.
Each product consists of
1) Raw Data Set: This data set consists of orbit, attitude data
(OAT) related to satellite position & platform. The other
important data set recorded by MSMR sensor is the raw
counts of 300 sample per scan (SDF) along with various
51 receiver junction temperatures and additional 60
samples of Calibration counts (Hot/cold) per scan to
quantify sensor performance per Calibration channels.
2) Antenna Temperature Data (ATD): This data product
consists actual temperature values seen by antenna
receiver using ground calibration coefficients and onboard
Hot/Cold calibration counts.
3) Brightness Temperature Data of 3 Grids (BTD): BTD
data product is grided data available in three resolutions