Present situation of spaceborne SAR
Nobuhiko Kodaira
Remote Sensing Technology Center of Japan
Abstract
The launch of spaceborne SAR are scheduled by ESA, Japan and Canada as E-ERS-1, J-ERS-1 and Radarsat in 1992, 1992 and 1994 respectively. SAR is reputed to be all weather type remote sensing instruct seat like other passive microwave radiometer.
In spite of this big advantage, present 3 programs are limited in single parameter SAR such as Cvv, Lhh, or Chh. So that the information obtained by these microwave instruments are restricted within a given application for each instrument. We should have correct understanding of the present SAR situation.
In this paper, heavy rain effect to X, C, L, P band SAR, inherent nature of the single parameter SAR data and the future polarimetric SAR will be described.
Introduction
SAR systems are considered to be one of the most unique remote seasing facilities because of the all - weather capabilities, independence of time of day and the penetration ability into the objects. Plenty of SAR data are obtained from spaceborne and airborne system, however, all of the spaceborne SAR data were single parameter and near future SAR schedule also shows that single parameter SAR is planned except SIR-C (Shuttle Imaging Radar-C) as shown in Tabel 1.
SIR-C is the first spaceborne polarimetric SAR planned by NASA. We are expecting the polarimetric SAR results from SIR-C experiment.
Table 1. Characteristics of Spaceborne SAR.
| | E-ERS-1 | SIR-C | J-ERS-1 |
Radarsat | EOS-SAR | SPOT-SAR |
| Frequency Polarization | C/W | L.C./Quad. X/Dual
| L/HH | C/HH | L/Quad. C.X/Dual | X/Dual |
| Resolution on the surface (m) | 30 | 60-20: Standard
30-10: High res.
| 18(3-looks) | 8*8(1-looks)
28*30(4-looks)
100*100(6-looks) |
20-30: High res.
50-100:Mid. res.
250: Global obs. |
4-20(1-20 looks) |
| Frequency Polarization | C/W | L.C./Quad. X/Dual
| L/HH | C/HH | L/Quad. C.X/Dual | X/Dual |
| Peak data rate(Mbps) | 165 | 46/channel
| 60 | 110 | 180 | --- |
| On board tape recorder | none | Yes
| yes | yes | yes | --- |
| Incidence angele(degree) | 23** | 15-55
| 38.5 | 20-45 | 15-40 | 12-64 |
| Swath width (km) | 90 | 15-90
| 75 | 50
100
400 | 30-50:High res.
100-200:Mid. res.
310-480:Glob. obs. | 20-40
(300-850) |
| Main purpose of observation |
Sea ice, Ocean |
Research
|
Geology Resources | Sea ice |
Sea ice
Vegetation,Sea ice
Soil mois.Geology |
Renewal resources
Topog. Soil mois. |
| Satellite altitude(Km) |
785 |
250
|
568 | 792 |
620 |
750 |
| Equatorial cross, time |
A. M. 10:30 |
Non-sunsynchronous
|
A.M. 10:30 | A.M. 6:00 |
P.M. 1:30 |
A.M. 10:30 |
| Antenna dimentions (m) |
1*10 |
2.8/0.8/0.4*2.1
|
2.2*12 | 1.8*15 |
2.6*10.9 |
2.2*8.1 |
| Transmit. peak power (kw) |
4.8 |
3.3/2.7/3.4
|
1.1 | 5 |
5.8 |
5 |
| Individuality |
Wave Mode |
Multi-Frequency/Polarization
| |
Scan SAR
Down Dusk Irbit | Scan SAR
Multi-FReq./Polar. |
Scan SAR
Focus Mode |
| Launch schedule |
1991 |
1991.2/1992.7
|
1992 | 1994 |
1996, 1998 |
1999 |
| Recurrence period(days) |
3* |
---
|
44 | 16(3) |
5 |
7 |
* Special observation in high altitude will be held with a time limit of 3 month after the launch.
** Incident angle will be changed experimentally by tilting the spacecraft itself.
