Engineering Telemetry Conversions ICD

Table of Contents

1.0  - Introduction

2.0  - Reference

3.0  - Active and Passive Analog Telemetry

3.1  - Items

3.2  - Conversions

4.0  - Bi-level Telemetry

4.1  - Hardware LED's

4.2  - Software LED's

5.0  - Serial Digital Telemetry

1.0 Introduction

2.0 Reference

Part Number	Version	Title
52100.200.063		Instrumentation Program and Command List (IP&CL)
D17387		AXAF-I Users' Guide to Remote Command and Telemetry Unit (RCTU)

3.0 Active and Passive Analog Telemetry

3.1 Items

Passive temperature transducers are read by the RCTU as voltages after the application of a 1.0ma current and converted to an 8 bit value with a scale factor of 20mv/bit. The active test points are read directly as voltages with the same scale factor.

Table 1.  

Mnemonic	Description	Conversion Type	Constants	Units	Special Case?
1CB[AB]T	Camera Body Temperature	RTD		C
1CR[AB]T	Cold Radiator Temperature	RTD		C
1DACT[AB]T	Collimator Temperature	RTD		C
1DAHH[AB]VO	DA Heater Bus Voltage	Linear	a = 0.156 b = 0	V
1DAH[AB]CU	DA Heater Output Current	Linear	a = 0.0200 b = 0	V
1DAH[AB]T	DA Heater Control Status	Discrete			yes
1DAH[AB]VO	DA Heater Output Voltage	Linear	a = 0.1198 b = 0	V
1DE28[AB]VO	DEA Input Voltage	Linear	a = 0.138 b = 0	V
1DEAMZT	DEA -Z Temperature	ACIS thermistor		C
1DEIC[AB]CU	DEA Input Current	Linear	a = -0.0704 b = 18.09	A	yes
1DEN0[AB]VO	DEA -6v Out	Linear	a = -0.0301 b = 0	V
1DEN1[AB]VO	DEA -15v Out	Linear	a = -0.0769 b = 0	V
1DEP0[AB]VO	DEA +6v Out	Linear	a = 0.0300 b = 0	V
1DEP1[AB]VO	DEA +15v Out	Linear	a = 0.0781 b = 0	V
1DEP2[AB]VO	DEA +24v Out	Linear	a = 0.120 b = 0	V
1DEP3[AB]VO	DEA +28v Out	Linear	a = 0.150 b = 0	V
1DP28[AB]VO	DPA Input Voltage	Linear	a = 0.138 b = 0	V
1DPAMYT	DPA -Y Temperature	ACIS thermistor		C
1DPAMZT	DPA -Z Temperature	ACIS thermistor		C
1DPIC[AB]CU	DPA Input Current	Linear	a = 0.0101 b = 0	A
1DPP0[AB]VO	DPA +5v Out	Linear	a = 0.022 b = 0	V
1HOPRAPR	Differential Pressure	Linear	a = 0.284 b = -21.13	torr
1HOPRBPR	Differential Pressure	Linear	a = 0.284 b = -19.10	torr
1MAHC[AB]T	Door Close Actuator Temperature	PSMC thermistor		C
1MAHO[AB]T	Door Open Actuator Temperature	PSMC thermistor		C
1OAH[AB]T	Starsys Housing Temperature	RTD		C
1PDEA[AB]T	PSMC DEA Pwb Temperature	RTD		C
1PIN1AT	PSMC Lid Temperature	RTD		C	yes
1SSMYT	SS -Y (DPA) Temperature	ACIS thermistor		C
1SSPYT	SS +Y (DEA) Temperature	ACIS thermistor		C
1VAHC[AB]T	Vent Close Actuator Temperature	PSMC thermistor		C
1VAHO[AB]T	Vent Open Actuator Temperature	PSMC thermistor		C
1WR[AB]T	Warm Radiator Temperature	RTD		C

Table 2.  

Mnemonic	Special Case
1DAH[AB]T	See DA Heater Control Status below
1DEIC[AB]CU	If (1DEP3[AB]VO <= 10) a = 0, b = 0
1PIN1AT	Divide count by 1.99 before converting.

3.2 Conversions

Within this section the term count represents the value that the RCTU reads. It ranges from 0 to 255. The term EU represents the value converted to the appropriate engineering units.

3.2.1 Thermistor in parallel with 5.05K, buffered inside PSMC; units of C

if ( count < 10 )
  EU = "--"
else if ( count > 176 )
  EU = "Cold"
else
  aa = ( 5050 * count ) / ( 6175 - count )
  qq = log( ( 152 * aa ) / ( 152 - aa) )
  EU = 1 / (1.074e-7 * qq * qq * qq + 2.372e-4 * qq + 1.4733e-3)
   - 273.16 + 15.0

3.2.2 RTD at 2K nominal; units of C

if ( count < 10 )
  EU = "Short"
else if ( count > 150 )
  EU = "Open"
else
  EU = -count * count * count * 3.181e-6 + count * count * 2.009e-3
   + count * 2.218 - 238.67

3.2.3 Thermistor in parallel with 5.23K (MIT) excited by 1ma; units of C

if ( count < 10 )
  EU = "Short"
else if ( count > 245 )
  EU = "Open"
else
  aa = ( count * 20 * 5.23e3 ) / ( 5.23e3 - 20 * count )
  qq = log(aa)
  EU = 1 / (1.074e-7 * qq * qq * qq + 2.372e-4 * qq + 1.4733e-3)
   - 273.16

3.2.4 Linear volts, current, temperature, or pressure according to aN + b formula

if ( count > 253 )
  EU = "+Error"
else
  EU = count * a + b

3.2.5 DA Heater Control Status

if  ( count > 224 )
  EU = "Cold"
else if  ( count < 32 )
  EU = "Hot"
else
  EU = "OK"

4.0 Bi-level Telemetry

4.1 Hardware LED's

Table 3.  

Mnemonic	Description	0 =	1 =
1STA4ST	Active BEP	A	B
1STA5ST	BEP is held in the reset state	Yes	No
1STA6ST	BEP FIFO is full	Yes	No
1STA7ST	BEP FIFO is empty	Yes	No

4.2 Software LED's

Table 4.  

Value	Software State
0	Watchdog Science active - Blink State A
1	Watchdog Science active - Blink State B
2	Watchdog Science idle - Blink State A
3	Watchdog Science idle - Blink State B
4	Science active - Blink State A
5	Science active - Blink State B
6	Science idle - Blink State A
7	Science idle - Blink State B
8	Initializing loaded code
9	About to patch up linked code
10	About to execute up linked code
11	Copying packets from up link
12	Waiting for first up link packet
13	Spare (formerly Ready to execute ROM code)
14	Spare (formerly Copying code from ROM to RAM)
15	BEP just reset

In the following, val = 1STA3ST*8 + 1STA2ST*4 + 1STA1ST*2 + 1STA0ST*1

5.0 Serial Digital Telemetry

.