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## Low Frequency Electromagnetic Compatibility Testing 

**of the**

**IMAGE Satellite**

**using the**

**Radio Plasma Imager (RPI) 3-Axis Receivers**

**Document Number. TR.9000001-02**

**Submitted to:**

**Southwest Research Institute**

**6220 Culebra Road**

**San Antonio, Texas 78228**

# Subcontract No. 83822

**Prepared by:**

**University of Massachusetts Lowell**

**Center for Atmospheric Research**

**600 Suffolk Street**

**Lowell, Massachusetts 01854**

**28 June 1999**

**TABLES OF CONTENTS**

1.0
SCOPE............................................................................................................1

2.0 REFERENCE
DOCUMENTS................................................................................1

2.1 SwRI
Documents.....................................................................................1

.

3.0 TEST
CONFIGURATION........................................................................\...............1

4.0 TEST MEASUREMENT
RESULTS...........................................................................3

4.1 Spacecraft
Susceptibility/Compatibility....................................................\........3

4.2 RPI/Science Instrument
Susceptibility.......................................\................\......12

**FIGURES**

3.1 EMC Test
Configuration...........................................................................\...............2

3.2 IMAGE being sealed up in the Battel EMC
Chamber......................................................4

4.1 Payload vs. Observatory baseline, top is low band, bottom is high
(7.1.3.1)...........................5

4.2 Charging Battery with 5A from Umbilical Power
(7.1.3.6)...............................................6

4.3 Deckplate Heaters on, highest current, top low band, bottom high
(7.1.3.2)............................7

4.4 AST on and PWM at 63%
(7.1.3.3)...............................................................\............8

4.5 Torque Rod Positive Current; Z-axis noise, 160-200 kHz
(7.1.3.4)......................................9

4.6 Torque Rod Negative Current
(7.1.3.4)...............................................................\......10

4.7 S-Band Transponder On (5 Watts), Torque Rod still On
(7.1.3.5)......................................11

4.8 Same as Fig 4.7, but with Torque Rod off
(7.1.3.6).......................................................12

4.9 MENA on in most active mode, low-voltage on HV
Supplies..........................................13

4.10 EUV in most active
mode....................................................................................14

4.11 FUV in most active
mode.....................................................................................15

4.12 LENA
active...................................................................................................16

4.13 HENA active (Low voltage on HV
supplies)..............................................................17

1.  SCOPE

This Electromagnetic Compatibility (EMC) test report defines the test
results from the EMC testing conducted at LMMS 12 -- 13 June 1999. The
object of the test was to characterize the electromagnetic environment
created by the IMAGE observatory and to demonstrate that the RPI
instrument and the IMAGE Observatory subsystems can operate adequately
within this environment. Specific goals of the testing were:

-   Establish an EMI noise floor for the RPI instrument in multiple
    observatory operating modes,

-   Demonstrate compatibility among the Science Instruments and the
    Observatory subsystems,

-   If necessary, to identify and characterize EMI emitters that
    interfere with RPI, and

-   Characterize the conducted emissions of the observatory.

The EMC testing was conducted in accordance with the approved
Electromagnetic Compatibility Test Procedure for the IMAGE Observatory,
8089-OBEMCTP-01, Rev. 0, Chg. 0.

2.  REFERENCE DOCUMENTS

2.1 SwRI Documents

> 8089-OBEMCTP-01 Electromagnetic Compatibility Test Procedure for the
> IMAGE Observatory

3.  TEST CONFIGURATION

To support the Payload level testing in March at Southwest Research
Institute, Battel Engineering fabricated a temporary screen room
enclosure designed to be a good enough shield against radiated EM waves
and local electrostatic fields to enable RPI to see its receiver noise
floor. Testing at SwRI confirmed that this was possible, so the chamber
was transported to Lockheed Martin Missiles & Space systems (LMMS) for
testing with the S/C systems added to the payload systems.

The configuration as used during the testing is shown in Figure 3.1.
Notable features of this configuration are that one solar array panel
input is replaced by the Solar Array Simulator (SAS), at which point the
umbilical power cable (W202) can be removed, leaving only the SAS and
one RS-422 cable connected through the walls of the EMC chamber. The SAS
provided power during the second day of testing, 13 Jun 99, however we
had occasion to run only on internal batteries on 12 Jun to investigate
sources of conducted emissions entering the chamber, and to find a short
in the DC power line filter. To also eliminate the RS-422 cable
connection, we used the Mass Memory Module to store about 25min worth of
telemetry while the cable was disconnected, allowing the S/C

![](media/image2.png){width="6.0in" height="8.000694444444445in"}

Figure 3.1 - EMC Test Configuration

to operate totally autonomously (i.e. no external cables connected).
During this run there was still an unacceptable amount of external
interference, which we concluded must be \"internal\" interference
generated by the S/C, since nothing was connected to the outside world.
However, after \"sniffing\" around with the active whip antenna as a
probe and the HP spectrum analyzer as a receiver, we identified the air
conditioning (A/C) hose (shown in Figure 3.2) and specifically the
spiral support wire inside the hose, as the conduit which conducted low
frequency RF into the chamber. This hose, used to cool the S/C battery,
was determined to not be required, and the S/C was operated without the
A/C hose for the remainder of the EMC testing.

Figure 3.2 shows the physical configuration, with the IMAGE satellite
inside the EMC chamber before the end wall was reinstalled and before
the A/C hose was removed. This picture also shows the single point for
cable entry in the near left corner. Also note the RPI antenna simulator
boxes installed in the far corners just before the \"antenna\" wire was
installed, connecting them to the deployer tip masses. Another two
boxes, shown on the floor, were later installed in the near end corners
so that four antenna wires could be connected. The -Z antenna was not
connected, and we placed a 1m wire into the +Z preamplifier input. It
was shown that taping this loose wire to the +Z \"stovepipe\" support
structure caused it to pick up about 20dB more noise, so it is important
to keep the antenna element well away from the structural walls (another
lesson learned for future testing, e.g. Observatory thermovac testing).

4.0 TEST MEASUREMENT RESULTS

1.  Spacecraft Susceptibility/Compatibility

Payload level testing in March at Southwest Research Institute verified
the interoperability of the RPI with the CIDP (Common Instrument Data
Processor) and the four other instruments that were available at the
time. The aim of the Observatory level series of tests was to establish
the interoperability of the additional systems, primarily, comprising
the S/C power, telemetry, attitude control, computers and data storage.
Since we had already made measurements at Southwest Research Institute
using the same Battel EMC chamber, we had a good baseline noise floor to
compare with our results at Lockheed. Using the EMC Test Procedure,
paragraph 7.1.3.1, we made a background measurement of the inside of the
EMC chamber with a minimum of new systems operating, specifically the
S/C PDU and SCU, which had to be on in order to power up the RPI and
CIDP.

1.  Figure 4.1, is an overlay of the March and June background noise
    data. It shows only a slight increase in the noise floor between 10
    and 60kHz. The peaks in this interference were correlated to noise
    monitored outside the chamber (especially the line at 20kHz on the X
    receiver) with an HP spectrum analyzer. Also, the fact that the
    amplitude of this noise is significantly greater on the X axis shows
    that it was carried in by cables passing through the EMC chamber
    wall near the -X antenna element. This same noise was two orders of
    magnitude larger on 12 June

![](media/image3.png){width="5.997222222222222in"
height="3.6743055555555557in"}

Figure 3.2 - IMAGE being sealed up in the Battel EMC Chamber. Note the
cable entry point with all cables wrapped in foil and grounded. The
cable run over to the umbilical consoles crossed the floor fully
enclosed in what we called cannelloni (which is stuffed pasta), while we
meant it to be calzone (which is a wrapped pizza with the goop on the
inside). It could also be cannolli, which is a stuffed desert pastry,
all the same idea.

before removing the A/C hose. The satellite was power by HP power
supplies through the umbilical connector A01J2, see Figure 3.1, until
early morning on June 13 when we switched over to input power from the
Solar Array Simulator (SAS), filtered by a line filter built by Battel
Engineering.

Although we had originally planned to command the S/C via the RF link,
this link had not been thoroughly debugged, so the RS-422 communications
cable going to the SCU (connector A01J1) remained connected during all
measurements shown in Section 2. Short tests were made with these
connectors disconnected (i.e. running on internal battery power) and no
difference was noticeable.

The only detectable interference sources from S/C systems were:

1.  A small 63kHz line and its 2^nd^ harmonic at 126kHz, when battery
    charge power was maximum. There were noticeable spikes only when the
    PWM duty cycle was greater than about 70%.

2.  The torque rod with positive current polarity showed a broad
    interference band between 160 and 200kHz.

3.  A small line came up at 75kHz whenever the S-band transponder was
    active.

![](media/image4.png){width="5.9944444444444445in"
height="4.355555555555555in"}

![](media/image5.png){width="5.9944444444444445in"
height="4.355555555555555in"}Fig 4.1 - Payload vs. Observatory baseline,
top is low band, bottom is high (7.1.3.1)

![](media/image6.png){width="5.9944444444444445in"
height="4.355555555555555in"}Figure 4.2 - Charging Battery with 5A from
Umbilical Power (7.1.3.6)

![](media/image8.png){width="5.9944444444444445in"
height="4.355555555555555in"}

Figure 4.3 - Deckplate Heaters on, highest current, top low band, bottom
high (7.1.3.2)

![](media/image10.png){width="5.9944444444444445in"
height="4.355555555555555in"}

Figure 4.4 - AST on and PWM at 63% (7.1.3.3)

![](media/image12.png){width="5.9944444444444445in"
height="4.355555555555555in"}

![](media/image13.png){width="5.9944444444444445in"
height="4.355555555555555in"}Figure 4.5 - Torque Rod Positive Current; Z
axis noise, 160-200 kHz (7.1.3.4)

![](media/image14.png){width="5.8in" height="4.214583333333334in"}Figure
4.6 - Torque Rod Negative Current (7.1.3.4)

![](media/image16.png){width="5.9944444444444445in"
height="4.355555555555555in"}

![](media/image17.png){width="5.9944444444444445in"
height="4.355555555555555in"}Figure 4.7 - S-Band Transponder On
(5Wattts), Torque Rod still On (7.1.3.5)

![](media/image18.png){width="5.9944444444444445in"
height="4.355555555555555in"}

Figure 4.8 - Same as Fig 4.7, but with Torque Rod Off (7.1.3.6)

1.  RPI/Science Instrument Susceptibility

We are glad to report that no spurious lines appeared when any of the
IMAGE instruments were operating. The tests in Texas had discovered a
series of lines that seemed to appear when the FUV instrument came on,
but upon retest it was shown that these lines appeared even when the FUV
was powered off. The source of the interference was never determined,
and now appears to have been brought in from outside the EMC chamber,
since several lines previously thought to be inherent in the RPI or CIDP
were not visible during the testing in California.

The following are scans with the PDU, SCU, CIDP and RPI operating in
addition to one instrument at a time, as noted.

### ![](media/image19.png){width="5.9944444444444445in" height="4.355555555555555in"}Figure 4.9 - MENA on in most active mode, low-voltage on HV supplies

![](media/image21.png){width="5.9944444444444445in"
height="4.355555555555555in"}

### Figure 4.10 - EUV in most active mode

### ![](media/image23.png){width="5.9944444444444445in" height="4.355555555555555in"}

Figure 4.11 - FUV in most active mode

![](media/image25.png){width="5.9944444444444445in"
height="4.355555555555555in"}

### ![](media/image26.png){width="5.9944444444444445in" height="4.355555555555555in"}Figure 4.12 - LENA active

![](media/image27.png){width="5.9944444444444445in"
height="4.355555555555555in"}

Figure 4.13 - HENA active (Low voltage on HV supplies)