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Earth observation system

Vinai Vorrawat
National Research Council of Thailand
196 Pahonyothin Road, Bangkhen, Bangkok 10230, Thailand

Abstract: The JERS-1 observation system can be divided into space segment and ground segment the space segments is JERS-1 satellite. The ground segment includes the tracking and control system a data acquisition and processing system. JERS-1 can carry two pieces of observation equipment, the synthetic aperture radar (SAR) and optical sensor (OPS) which composed of two radiometer the visible and near infrared radiometer (VNIR) and short wave infrared radiometer (SWIR) JERS-1 composed of these observation equipment. Mission data recorder (MDR), Mission data transmission (MDT) and subsystems for solar paddle, attitude and orbit control and thermal control. The satellite revolves in 96 minutes around the earth. It makes 15-1/44 revolutions per day and returns to the same orbit every day.

1. Introduction
When 8 GHz band receiving subsystem is used to receive a JERS-1 signal and checking the operation of a receiving system the subsystem is operated either through remote control by an antenna subsystem or local control by the controller of a 8GHz band main receiver. The subsystem does not require much complicated operation and can be set to most operating modes of the subsystem through remote control, enabling the subsystem unattended during normal operation.this paper descries outlines of the operation procedures for startup of the whole subsystem, receiving the signals and stopping power base on fig 1 for details refer to the operation introduction in relevant equipment. 8 GHz band main low noise The status can only be checked by the antenna subsystem.8 GHz band frequency down converter (X-D/C) (S/X -D/C) set the power on/off control switch to remote. The X-D/C status can be also checked at the antenna system. 8 GHz band main receiver (X-RX). The normal operation mode is remote (remote control from the antenna subsystem.) 8 GHz band main receiver (X-RX). The normal operation mode is remote (remote control from antenna system) . The following element should preferably be monitored during reception a reception level (AGC level.) angle error voltage. Lock status and the X-RX status can be also checked at the X-RX status can be also check at the antenna system. 8 GHz band receiving system. The receiving subsystem operations check using the X-cal before reception is not necessary unless otherwise specified. However recommences that the check be perform as it is an effective way of ensuring the reception.

X-LNA : 8 GHz Band Low-noise amplifier
X-D/C : 8 GHz Band frequency down converter
X-RX : 8 GHz Band main receiver

– These procedures may not be performed.

Figure 1 Flow Chart Overall Operation Procedure
2.Operation
Table 1. Lists the operation precautions for each equipment

No. Equipment name
1. 8 GHz band low-noise the status can only be checked by the antenna subsystem.
2. 8 GHz band frequency down converter (X-D/C) (S/X-D/C)
– Set the power ON/OFF control switch to REMOTE
– The X-D/C status can be also checked at the antenna subsystem.
3. 8 GHz band main receiver (X-RX)
– The normal operation mode is REMOTE (remote control from the antenna subsystem)
– The following items should preferably be monitored during reception
– Reception level (AGC level)
– Angle error voltage
– Lock status
– The X-RX status can be also checked at the antenna subsystem.
4. 8 GHz band test equipment (X-CAL)
– Before reception, check that the test signal output is OFF.
– The status can be also checked at the antenna subsystem .
5. 8 GHz band receiving subsystem
– The receiving subsystem operation checks using the X-CAL before reception is not necessary unless otherwise specified.
– However, NEC recommends that the check be performed, as it is an effective way of ensuring the reception.

3. Troubleshooting

3.1 Abnormal condition
The section descries the abnormal conditions and troubleshooting of troubles in the receiving subsystem as well as associate with other subsystem. To find and handle troubles in each equipment, refer to relevant pages of the manual for each equipment.
Abnormal condition
No image output on the quick looks equipment after a passage of the satellite arrival time.

The antenna is oriented to the arriving satellite, the programmed tracking operation normal and the predicted value for the orbit correct.

Figure 3 Flow chart for Troubleshooting
3.2 Abnormal condition 2
The satellite reception is performed normally but the operation fails with a testing equipment.

Figure 3 Flow chart for Troubleshooting
3.4 Measure in case of trouble
When a trouble is detected the instructions below:
– Turn off the power of the equipment in trouble installed in the antenna center ring; The D/C and U/C should be powered off at the main receiver.
– Inspect the equipment in trouble according to the maintenance manual for that equipment, and notify NEC of the details of the trouble.
Level control
Proposes of the Test
To confirm the control function of output level
Performance objective
(a) Control by means of the step attenuator.
(b) Remote control can be performed at the operation room.
(c) Output level
Range: -110 dBm (1 dB step).(This level is calculated on condition that the test RF signal is supplied to 8 GHz Band Low noise Amplifier input terminal.)
Setting: The deviation is less than 2-dB accuracy
(d) Test Equipment
signal generator : HP– 8863 A
Power meter : HP- 436 A
Controller in the 8 GHz band main receiver

Figure 4 Measurement (X-BAND) 8150MHz and 8350 MHz
Test procedure
Step 1 set the signal generator as follows
Frequency 140 MHz
Level –7 dBm 1 dB (50 ohm)
Step 2 Supply the signal to TEST UP CONVERTER.
Step 3 set controller as table 1
Step 4 Measure the output at “RF OUT PUT SUM” connector.

  1. The level at LNA input terminal is 35 dB (nominal) less than the output level at “RF OUTPUT SUM” connector of MSK TEST UP CONVERTER.
  2. The level at “ RF OUTPUT DIFF” is 9 dB (nominal) less than have “RF OUTPUT SUM”

Table 1 Controller Parameter setting

ITEM PARAMETER
CONTROL MODE LOCAL
OUTPUT ON
FREQUENCY 8150M or 8350M
LNA INPUT LEVELS 70-110dBm the Level more than –70dBm and the level less than 110dBm are set at –110dBm.
LEVEL CONTROL (X-BAND) output frequency 8150 MHz

LNA INPUT LEVEL (dBm) U/C OUTPUT LEVEL (dBm) ATTENUATION (dB)
-70 -35.93 0
-71 -36.97 1.04
-72 -37.92 1.99
-73 -38.94 3.01
-74 -39.96 4.03
-75 -40.97 5.04
-76 -41.94 6.01
-77 -42.99 7.06
-78 -44.00 8.07
-79 -45.06 9.13
-80 -46.16 10.23
-90 -56.16 20.23
-100 -66.13 30.20
-110 -76.21 40.28
Maximum deviation +0.28dB at –110 dBm –0.01 dB at –72 dBm 0.29 dBp-p

LEVEL CONTROL
(X-BAND)
Output frequency 8350 MHz
LNA INPUT LEVEL (dBm) U/C OUTPUT LEVEL (dBm) ATENUATION (dB)
-70 -35.80 0
-71 -36.83 1.03
-72 -37.77 1.97
-73 -38.81 3.01
-74 -39.81 4.01
-75 -40.84 5.04
-76 -41.84 6.04
-77 -42.87 7.07
-78 -43.89 8.09
-79 -44.90 9.10
-80 -55.85 10.13
-90 -65.85 20.05
-100 -65.85 30.05
-110 -75.85 40.05
Max deviation 0.13dB at 80dB -0.03dB at 100dB 0.16 dBp-p

Reference

  • Reception and recording facility MOS-1 Thailand Station
  • Maintenance Test Data, NEC Corporation, March 1995
  • Training Manual (in Thailand) on Reception and Recording Facility
  • (MOS-1 Thailand Station), November 1987, NEC Corporation Tokyo, Japan