ACC-E Flight model (at Titan temperature) ========================================= 1bit with high gain 0.017578125 V 1bit with high gain (at Titan temperature) 2.054 N All Huygens data is taken at High Gain (transition to medium gain is 1.89 V or 218.95 N) ACC-E hardware threshold required input force (at Titan temperature) 7.18735 N "N.B. For details of the filter effect of SSP electronics circuit please see ""Huygens data calibration report"" by G. Kargl, March 2005." ACC-I Flight model ================== Range for FM system plus and minus 90.354 g 0 counts minus 5 V 2048 counts 0 V 4096 counts plus 5 V 1 count 0.04412 g 80 count threshold 3.5296 g "N.B. For details of the filter effect of SSP electronics circuit please see ""Huygens data calibration report"" by G. Kargl, March 2005." Sampling for Mode 4 ------------------- "Sampled at 500 Hz for 512 samples, transmitted at 12 bit" Threshold crossing position is normally at sample 64 "N.B. Software threshold is 80 counts relative to ""ACC-I Offset"" as frozen at start of Mode 4 (given in SSP Housekeeping data)" Sampling for other Modes (1,2,3,5 & 6) --------------------------------------- Sampled at 500 Hz for first 0.4s of every 1.0s "Mean, Max and ""Variance squared"" transmitted for these 200 samples every 1 sec" API-V Flight model ================== Separation of API-V sensor crystals on FM Top Hat 0.1289m 1 count 250ns Velocity (m/s) on FM Top Hat with FM electronics 0.1289/(counts * 0.00000025) N.B. The measured speed of sound is not identical in both directions. This might in part be due to physical differences due to probe rotation for example. Although in reality the difference is mainly due to the two sensors not being identical in their performance as transmitters and receivers. API-S Flight model ================== Frequency 14.71 kHz Nominal pulse width 10.3 ms Short pulsewidth 2.0 ms "Used if Status Flag (CDMU B14) set to 1 in Proximity Mode (expected below 1km altitude IF radar altimeter working and probe DDB bit set to ""measured altitude"")" Nominal Output power (Pt) 104 dB (with respect to 20 micro-Pascal) Sensor area (A m^2) 2E-3 sq m (10 off 14mmx14mm piezo-electric crystals) Range ----- To convert API-S time (millisec) into range we need to use the velocity of sound derived from API-V N.B. There is negligible difference between API-V measured velocity (at 1 MHz) and API-S (at 14.71 kHz) Range = [ time (s) * velocity (m/s)]/2 N.B. For echo compression algorithm see Software User Manual. Sensor Beam Pattern ------------------- "Sensor Beam Pattern is a zeroth order Bessel function (Jo(sin?)/sin?), with orthogonal half angles of 14 degrees and 20 degrees." "N.B. For further information on API-S analysis see ""Physical properties of the Huygens landing site from the Surface Science Package Acoustic Properties Sensor (API?S)"" by M. C. Towner et al., accepted for publication by Icarus on 2nd August 2006." DEN Flight model ================ The DEN measurement is the voltage change when the sensor is immersed from a cold nitrogen atmosphere (at a temperature around 94 K) into a cold surface liquid (at a temperature around 94 K) - this reduces the effect of temperature drift to a minimum. Sensitivity for FM DEN sensor (in temp range 90 K to 100 K) and Earth g (9.80665 ms^-2) 600 kgm^-3/Volt Sensitivity at Titan gravity (1.345 ms^-2) =(9.80665/1.345)*600= 4374.713755 kgm^-3/V One Bit sensitivity at Titan is: 10.67867628 kgm^-3 Sensor read to 12 bits (average of 8 samples every 50 microseconds) range +5 V to -5 V = 4096 bits 1 count/bit = 2.441 mV PER/CON Flight model ==================== PER --- PER Diode Volts (DV) = counts*5/2048 PER_T (K) = 518.07-(98.302*DV) + (5.4764*DV^2) - (1.1372*DV^3) "Calculate Er =1 Voltage, V0 = 4.0229 - 0.084+ (0.0647*x)+ (0.1276*x^2) + (0.0861*x^3) - (0.1006*x^4)" where x is a normalised temperature = (PER_T(K) -150)/150 "PER Volts, PV = [(Percount- Peroffset count)*5/2048]" "Relative Permittivity, Er = 1 + (PV-V0) * 40.508/121" CON --- Resistance Between PER plates (Mega Ohm) = ((1.005*X) - 505) / (1000 - X) "where, X = (CON_OUTPUT(INT) * 0.1369536) + 746.8406" N.B. The saturation value for CON_OUTPUT(INT) is 1845. This is approximately equivalent to 4.5 Volts and is expected for a high impedance or open circuit measurement. REF Flight model ================ Refractive Index range: 1.250 to 1.450 Resolution (1 pixel): 0.0005 Pixel 0 = R.I. 1.250 Pixel 399 = R.I. 1.450 Internal Illumination mode - Maximum of dI/dx gives Refractive Index External Illumination mode - Minimum of dI/dx gives Refractive Index Only use pixels 0 to 399 for dI/dx Refractive Index is linear between pixel 0 and pixel 399 Pixel level output range 0.0 to 2.50 V "Linear photodiode array output is sampled to 12 bits but compressed to 8 bits transmitted (note saturated pixels will ""roll over"" and look like zero or very small signal)" THP Flight model ================ Resistance & Temp from Low current measurements current (A) Amp offset Amp gain k l m c Wire 1 0.000781 -0.0055 82.95 -0.063 1.5552 17.001 41.095 Wire 2 0.000781 -0.015 83.114 0.0031 0.7828 18.923 39.164 Wire 3 0.00031 -0.0103 83 -0.0005 0.0641 1.9238 45.532 Wire 4 0.00031 -0.0135 83.084 -0.0012 0.1279 0.0492 62.127 "To calculate initial wire resistance and initial temperature use the equations below, and the relevant values and constants from the table above for that particular wire:" "Initial Wire Resistance, Ro (Ohms) = (Vinit - Amp offset) / (current * Amp gain)" "Initial Wire Temperature, To(K) = k.(R^3) +l.(R^2)+m.(R)+c" "(where Vinit = initial (low current) measurement in Volts, given in PDS data set)" Delta Resistance (dR) & Temp from high current measurements current (A) Amp offset2 Amp gain Amp offset1 (V) B Wire 1 0.100345 -0.0055 82.95 3 25.42 Wire 2 0.100345 -0.015 83.114 3 25.601 Wire 3 0.010355 -0.0103 83 3 4.325 Wire 4 0.010355 -0.0135 83.084 3 4.2 dR (Ohms) = (V + Amp offset1 - Amp offset2) / (current * Amp gain) dT(K) = B.(R) "where V= voltage measurement after high current step, given in PDS data set" TIL Flight model ================ TIL-X THETA=((TILXH*2.5/4.5) -1.246))/0.017395 TIL-Y THETA=((TILYH*2.5/4.5) -1.2581))/0.016649 Angle between TIL-X and probe +Zp axis is nominally 30 degrees Rotation clockwise is positive for both Angle between TIL-Y and probe -Yp axis is nominally 30 degrees Rotation clockwise about TIL-Y gives more positive output (clockwise around +Yp is defined as positive for probe rotation) N.B. Sensor output saturates at around 60 degrees. N.B. TILXH is the reading for the TIL-X sensor for the positive cycle of the drive pulse. The sensor is also read during the negative cycle giving TILXL. The magnitude of TILXL could be used to calculate angle by replacing TILXH in the equation above. There is the same measurement for the TIL-Y sensor, with the magnitude of TILYL being a replacement value for TILYH in the equations above. In reality the High and Low readings are taken just 1 millisecond apart and therefore rarely differ. The exception is in SSP Mode 4, when a software processor glitch occasionally gives "frozen" values for around 10 consecutive samples. Since this occurs at different mission times for TILXH and TILXL (or for TILYH and TILYL), the Low data can be useful in this mode. FM Housekeeping Temperatures ============================= Linear fits taken from SSP FM Temperature Sensor Calibration Data Polynomial fit for FM PER Diode Temp Diode Output (V) = counts*5/2048 Temp (K) = m*(Temp Diode Output in V) + C Sensor m C Sensor Location Sensor Type THP_T -81.246 425.3 On plate of THP sensor at top of Top Hat cavity 1N6642 diode REFSEN_T -81.3 427.76 On REF pcb next to linear photodiode array 1N6642 diode REFTIP_T -83.33 433.58 "On REF prism tip, in Top Hat cavity" 1N6642 diode REF_BASE_T -81.3 422 "On REF prism base, in Top Hat cavity" 1N6642 diode TOPHAT_T -92.59 449.47 "In Top Hat foam, near reference mounting foot" 1N6642 diode THP_ADC_T -80 427.74 On ADC chip on SSPE1 16-bit board 1N6642 diode CONVT -83.33 436.425 On 5 V DC-DC converter IC on SSPE6 Power Supply board 1N6642 diode TILT_T 75.75 -1.659 On inside of SSPE box under TIL sensor AD590LF/883B SSPEBOX_T 75.75 -3.136 On inside of SSPE box near ACC-I and reference AD590LF/883B mounting foot 2V5REF_T 526.336 0 In IC on SSPE3 (12-bit board) "IC on SSPE3 electronics board" PERT_T see below In PER sensor GFRP structure near centre of Top Hat side wall 2N2222 diode For PER_T use following equation: PER Diode Volts (DV) = counts*5/2048 PER_T (K) = 518.07-(98.302*DV) + (5.4764*DV^2) - (1.1372*DV^3) TIL FM Housekeeping Reference Voltage monitors ======================================== Offset Description Mnemonic Notes (Bytes) 81 2.5v REF Mon 2V5   Actual voltage = Monitor Voltage x 1 84 4.5v REF Mon 4V5   Actual voltage = Monitor Voltage x 1.124 84 -9v Ref Mon M9V   Actual voltage = Monitor Voltage x 2.241 87 +12v Mon P12V   Actual voltage = Monitor Voltage x 3.010 87 -12v Mon M12V   Actual voltage = Monitor Voltage x 3.010 90 +5v Mon P5V Typical value 3.857 V 90 Test Input Via 12 Bit A/D TEST Typical value -0.083 V 93 THP Voltage Ref - Gas (Via 12 Bit) VREFG Typical value 2.249 V 93 THP Voltage Ref - Liquid (Via 12 Bit) VREFL Typical value 2.249 V 96 ACC-E Pre-amp Output ACCEPRE Typical value 0.005 V 96 DEN Offset DENOFF 99 CON Offset CONOFF 99 PER Offset PEROFF 102 "TIL Excitation X, +ve" TOPXH 102 "TIL Excitation X, -ve" TOPXL 105 "TIL Excitation Y, +ve" TOPYH 105 "TIL Excitation Y, -ve" TOPYL 108 "TIL Offset X, Top" TOPXO 108 "TIL Offset Y, Top" TOPYO 111 TIL Offset X TLXO 111 TIL Offset Y TLYO 114 ACC-I Offset ACCIOFF Varies with temperature. Used as zero level for ACC-I impact detection algorithm in Mode 4 - value frozen at end of Mode 3. 116 Errors ERRORS 117 Status Byte - (Port C + A?) STATBYTE 118 THP Voltage Ref - Gas (Via 16 Bit) VREFG16 Typical value 2.490 V 120 Test Input via 16 Bit A/D TEST16 Typical value 0.002 V 122 +5v Mon Via 16 Bit A/D P5V16 Typical value -3.876 V 124 End Sync = 0x9999 ENDSYNC "N.B. These values are included for reference only, it is not expected that they will be of use for mission data analysis" N.B. For details see Software User Manual