The Solar Occultation for Ice Experiment SOFIE Mark

The Solar Occultation for Ice Experiment SOFIE Mark Hervig, SOFIE Deputy PI Larry Gordley, SOFIE PI GATS Inc. SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 1

Introduction SOFIE was designed to measure PMCs and the environment in which they form Measurement challenges: PMCs occupy tenuous altitudes: 83 km / 0. 006 mb PMC particles: 50 nm radius / 80 cm-3 concentration PMC signals are low 100 times lower than PSCs 1000 times lower than cirrus Gas signals are 100 times lower than in the stratosphere Solar Occultation can meet these challenges: Brightest source Relative measurements SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 2

Solar Occultation The sun rises and sets relative to the spacecraft (30 times a day). SOFIE stares at the sun, measuring profiles of solar intensity during each rise & set SOFIE signals yield atmospheric transmission, a relative measurement: SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 3

Measurement Objectives Measurements in specific wavelength regions target specific gases or particles. Measured transmission profiles are used to retrieve geophysical parameters: Temperature O 3, H 2 O, CO 2, CH 4, and NO mixing ratios PMC extinction Vertical profiles from the tropopause to over 100 km, with 1. 5 km resolution SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 4

Measurement Geometry SOFIE sample volume length = 280 km Excellent vertical resolution ZT Long horizontal path length RE SOFIE vertical resolution, Z = 1. 5 km SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 5

Optical Layout SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 6

Differential Absorption Measurements Each SOFIE channel uses two detectors to make three measurements: 1. Strong band absorption 2. Weak band absorption 3. Difference signal, V = weak – strong V reduces or eliminates common mode noise: atmospheric interference, tracking jitter, chopper noise, sun spots Simultaneous measurements of: PMCs Temperature H 2 O SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 7

Channel Description Channel 1 2 3 4 5 6 7 8 Band / Target Center Wavelength ( m) 1 / O 3 s 0. 291 2 / O 3 w 0. 330 3 / PMC s 0. 867 4 / PMC w 1. 04 5 / H 2 O w 2. 46 6 / H 2 O s 2. 62 7 / CO 2 s 2. 79 8 / CO 2 w 2. 94 9 / PMC w 3. 06 10 / PMC s 3. 12 11 / CH 4 s 3. 38 12 / CH 4 w 3. 48 13 / CO 2 s 4. 32 14 / CO 2 w 4. 65 15 / NO w 5. 01 16 / NO s 5. 32 Difference Signal Gain Detector 30 Si. C, PV 300 Ge, PV 96 Hg. Cd. Te, PC 110 Hg. Cd. Te, PC 120 Hg. Cd. Te, PC 202 Hg. Cd. Te, PC 110 Hg. Cd. Te, PC 300 Hg. Cd. Te, PC SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 8

Retrieved Parameters ØVertical resolution: 1. 5 km (over-sampled at 150 m) ØHorizontal resolution: 280 km 4 km Retrieval Precision worst case estimates Altitude Range (km) PMC Interference (signal fraction) T 2. 8 K 1 - 100 0% O 3 1 ppbv 15 - 100 50% H 2 O 0. 15 ppmv 15 - 100 0% CO 2 5. 3 ppmv 15 - 100 0% CH 4 30 ppbv 15 - 95 90% NO 2 107 cm-3 80 - 120 20% PMCs V, 10 -7 V, 10 -9 km-1 cloud - SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 9

Geographic Coverage AIM orbit is polar, noon - midnight crossings SOFIE provides 30 occultations (soundings) per day 15 sunrises in the south, 15 sunsets in the north Consecutive measurements are separated by 1. 6 hours & 900 km sunrises SOFIE coverage during one year sunsets SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 10

Sun Sensor Megapixel FPA, 701 nm wavelength Pointing precision is 0. 5 arcsec Measurements of solar extent provide refraction angle Refraction angles are used to retrieve temperature profiles SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 11

PMC Measurements Retrievals of particle extinction (optical cross section / volume = km-1) 10 wavelengths from 0. 33 - 5 m • Radiometer signals (10 's) = 0. 330, 0. 867, 1. 04, 2. 46, 2. 94, 3. 06, 3. 12, 3. 48, 4. 65, and 5. 01 m Digitization limit = 1. 1 10 -7 (km-1) • Difference signals (2 's) Ch 2: = 0. 95 m, gain = 300, digitization limit = 4 10 -10 (km-1) Ch 5: = 3. 09 m, gain = 120, digitization limit = 9 10 -10 (km-1) SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 12

Integral PMC Properties The infrared PMC signal is due to absorption which is directly proportional to r 3 and therefore particle volume density, Vice, Vice = C ( ) (1)) Where C is a constant, ( ) is extinction in km-1, and Vice is in m 3 cm-3. Constants for Equation 1. ( m) C 2. 94 964. 9 3. 06 369. 1 3. 19 838. 8 4. 63 17758. 3 SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 13

PMC Size Distribution Retrievals PMC measurements spanning 0. 3 to 5 microns are key will allow retrievals of complete PMC size distributions. Retrieval considerations: Particle shape: Spherical (Mie) Non-spherical (T-matrix) Size distribution form: Lognormal Gaussian Discrete (# bins = # 's) SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 14

Cosmic Dust / Smoke • Cosmic dust measurements are sparse and incomplete • Current understanding based on scant observations combined with theory e. g. , Hunten et al. [1980], Kalashnikiva et al. [2000]; Rapp et al. [2002] PMC volume densities are about 0. 08 m 3 cm 3 SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 15

Smoke Signals in SOFIE Data Predictions based on CARMA smoke model [Rapp et al. , 2002] SOFIE channel #2 (0. 86 & 1. 03 m) Radiometer signals are below the digitization limit. V signal of 90 counts at peak, but 30% of this is due to molecular scattering SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 16

Correlative Measurements AIM is seeking correlative measurements: Validation and enhanced science Altitude: Focus on mesosphere, but SOFIE observes trop - 100 km Latitude: 65 - 85 north & south Time: focus on polar summer, desire other times Measurements: PMC, PMSE, dust, aerosols, T, O 3, H 2 O, CO 2, CH 4, NO The AIM website (aim. hamptonu. edu) will provide Measurement locations Coincidence alerts (automated) Coincidence criteria will vary depending on the geophysical parameter SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 17

Summary l. Continuous coverage of 65 - 85 latitude, north & south l. Measures profiles of: Temperature O 3, H 2 O, CO 2, CH 4, and NO mixing ratios PMC extinction l. SOFIE online: sofiedata. org l. AIM online: aim. hamptonu. edu SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 18

Backup slides follow SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 19

Sun Sensor ØTwo basic components: Fast steering mirror 1024 x 1024 focal plane array (FPA) Ø 701 ( 11) nm wavelength Ø 7. 14 arcsec pixel dimension, 18 arcsec FOV (FWHM) ØS/C is solar-pointing during SOFIE occultation SOFIE pointing should only manage S/C jitter Ø Testing indicates 0. 5 arcsec precision SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 20

System Technical Resources RESOURCE POST CDR CBE MEASURED MATURE ALLOTMENT Mass 36. 7 kg (minus bus cabling fixtures) 38. 0 kg 42. 2 kg Envelope Controlled by MICD Average Power 67. 7 W [50. 5 W Electronics Unit, 17. 2 W Instrument Unit] 52 W [38. 8 W Electronics Unit, 13. 2 W Instrument Unit] 85. 2 W Peak Power 107. 6 W 85 W Pin-puller Peak Power Survival Heater Average Power 32. 2 W for < 0. 5 sec, [130 m. W Pre and Post Fire] 28 W during < 0. 5 sec Fire 15. 2 W Survival Heater Peak Power 62. 8 W 59 W Daily Data Volume 168 Mbits/day 200 Mbits/day SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 21

Commissioning Phase SOFIE commissioning will use SDL & GATS personnel SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 22

Channel Separation Module SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 23

SOFIE Overview ØVertical resolution: 1. 5 km, over-sampled at 150 m ØHorizontal resolution: 280 km 4 km Ø 16 bit digitization ØRetrievals: Temperature / Pressure O 3, H 2 O, CO 2, CH 4, NO PMCs (10 wavelengths from 0. 330 to 5. 01 m) SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 24

Implications of MAGIC Dust Measurements • Mesospheric Aerosols Genesis Interaction and Composition (MAGIC) Rocket-borne particle collector using a carbon impact grid Lab analysis reveals particle size, concentration, and composition • MAGIC flight over Wallops indicates cumulative smoke concentrations of 106 cm-3 Cumulative over radii from 1 - 3 nm and altitude from 76. 7 - 93. 5 • CARMA model (Markus Rapp) gives cumulative concentrations of 2. 2 104 cm-3 MAGIC concentrations are 46 times greater than CARMA model SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 25

SOFIE Signals Considering MAGIC Concentrations CARMA smoke concentrations were scaled by 46 at all sizes and altitudes SOFIE channel #2 (0. 86 & 1. 03 m) radiometer signal is 30 times higher than digitization limit V signal of 2800 counts at peak SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 26

System Calibration Overview System Functionality Requirement Result Nonlinearity < 0. 5% calibration uncertainty on all bands RSR – Out of Band Energy Desired < 1% < 0. 5% on all bands Thermal Stability < 6400 Counts < 30 Counts Pointing Ability < 15 arcsec < 2 arcsec (elev) Pointing Knowledge < 1 arcsec < 0. 4 arcsec (elev) Signal to Noise Science Time Stamp Accuracy Measured margin > 1 (except NO channel, 0. 9) < 2. 5 ms < 100 us SOFIE GATS Mark Hervig, CEDAR Meeting, 20 June 2006 27