telis progress meeting, oberpfaffenhofen, 3. december 2007 telis terahertz limb sounder

TELIS Progress Meeting, Oberpfaffenhofen, 3. December 2007

TELISTeraHertz Limb Sounder


Agenda9:30 Welcome, Status of Telis: Summary of IMK integration campaigns, mechanics,

electronics, software (M. Birk, G. Wagner)10:00 Status of DLR channel (N. Suttiwong)10:15 Status of SRON channel (G. de Lange, P. Yagoubov)10:30 Status of RAL channel (N.N.)10:45 Coffee break11:00 Radiometric accuracy: sideband ratio, autocorrelator (M. Birk)11:30 Time schedule before Teresina campaign (M. Birk)12:00 Scientific capabilities of TELIS: DLR channel (M. Birk), SRON channel (N.N.), RAL

channel (N.N.)12:45 Lunch14:00 Scout scientific goals (H. Oelhaf)14:15 Planning of Teresina campaign, tuning science with MIPAS team, discuss

measurement plan (all) 15:15 Planning of Kiruna campaign (all)15:30 Coffee break15:45 Funding, campaigns, etc. after Kiruna (all)16:15 TELIS on HALO (M. Birk)16:30 Spare time17:30 End of meeting


Status after 2nd integration campaign

Successful integration, pointing, EMC, TV test

Problems

• Leak in He constant pressure control

• Rate gyro not functional

• Light switches not functional

• Calibration blackbody T sensors not functional

• Measurement time efficiency insufficient

• Radiometric accuracy not established

• Faulty power supply for autocorrelator

To be solved for test flight

To be solved for flight with scientific results


Open issues and modifications

Mechanics

• Cabling between movable and static telescope parts

• Connector plate of autocorrelator unit modification

• Indium seals for flanges, heat exchange unit

• Radiation shield for telescope and cables



Electronics/cabling

• Line drivers for MORABA card digital outputs

• Ground cables for control lines

• New DC/DC box for autocorrelator unit from SRON

• 5V, 6A DC/DC converter for autocorrelator improved

• Safety circuit for 1.8 THz channel LO

• Filters for DC/DC converters in analogue and digital rack

• Suitable batteries for analogue rack

• Resistor network for gate Voltage



Software

• Implementation of SRON driver

• HEB current monitor for PC/104

• On-board backup

• Adaption of 8 Gbyte Flash ROMs

• TM/TC test in Toulouse, round 2

• UDP ?

Thermal design

• Iteration of radiator areas

• Coating of radiator areas


Radiometric accuracy

• Requirement: 1% true radiance

• Investigation: Gas cell measurement of opaque lines

• Needed: Sideband ratio – all three receivers measure double sideband mode

• Exception: Two opaque lines from both sidebands superimposed at same IF frequency


LO=16,961751

150

170

190

210

230

250

270

290

310

330

4000 4200 4400 4600 4800 5000 5200

Frequency, MHz

Bri

gh

tnes

s T

emp

erat

ure

,K

17:PE=4 15:PE=0

DLR channel, methanol, red: PE attenuator, blue: no attenuator

• Peak intensity wrong, 15 K instead of 300 K

• 11.5% line intensity error

• At first attributed to non-linearity in IF chain

DLR Measurements August 2007


RFpower & ACS

0

2000

4000

6000

8000

10000

12000

14000

16000

50 100 150 200 250 300

Temp (from Themometer), K

ab

s P

ow

er

0

0,2

0,4

0,6

0,8

1

1,2

Po

wer

, mW

abs(ACS) RFpower Linear (RFpower) Linear (abs(ACS))

DLR measurements October 2007

The IF was found to be perfectly linear


SRON channel, OCS, blue: 0.17 mb, black: 10.46 mb

SRON channel, OCS, olive: 10.5 mb, red: 31.26 mb, green: 60.02 mb, blue: 104.12 mb, cyan: 60.02 mb

SRON measurements November 2007


SRON measurements• Line intensity error 25%

• Spectral shape garbled, artefacts present – more serious error than intensity scaling error

• Apparantly severe error only when:

•Spectral IF gain varies by more than 5dB?

•Broad line is present

• Autocorrelation and quantization correction of broad features numerically simulated --- should be no prinicipal problem for autocorrelator

• SRON is currently fixing IF problem


Detected autocorrelator spectrum

SRON DLR


DLR measurement November2007

Measurement at 5 mb (green, 13 spectra averaged), 10 mb (red, 41 spectra)


Conclusion on autocorrelator problems

• The severe error (artefacts, spectrum garbled) is not linked to broad lines

• Remaining line scaling error can be attributed to a lag 0 error

• Modelling has shown: Quantization error changes ratio of line contrast to noise floor

• Noise floor information in lag 0, line information in all lags

• Error propagation into calibrated scene leads to observed spectrum

• Correction may be feasible

Open questions:

• Chip-dependence of scaling error?

• How does the error depend on the autocalibration?

• How does the error depend on spectral shape?

• Why does autocorrelator not work for strongly varying IF gain + broad line


Outlook for autocorrelator problems

• Noise source + synthesizer with ACS and spectrum analyzer

• OCS measurements after IF of SRON channel is fixed

• Excerpt of relevant data will be sent to Omnisys

• Other experts involved: Chalmers, SRON


Sideband ratio determination

Sideband ratios may depend on• Microwindow• Frequency within microwindow• LO power• Mixer bias• In case of standing waves: outside pressure, temperature

Requirement for double sideband measurement• Fabry-Perots fringes reduced to percent level


Two methods:

1. Gas cell measurements with sample/without sample with two different radiation sources behind cell

Requires a spectrometer without problemsRequires lines covering range of interest

2. Bruker measurements

Method established

Requirement: Overspill of antenna beam by Bruker AΩ

Current status

No sideband ratios for level 2 processing determined


Sideband ratios for different LO and mixer bias settings


Sideband ratio variations for different LO and mixer bias settings


First sideband ratio measurements of THz channel 30.11.2007

• Diplexer tuning not optimised

• Problems with Bruker

• Only tentative results

• Spectral sideband variations ca. 6%, possible Fabry-Perot with 23 cm spacing

• Coincides with distance diplexer – HEB rooftops

• Should go away for better diplexer tuning


Sideband ratio THz channel, LO = 1839.75 GHz = 61.367 cm-1,

Pink: USB/LSB, red: USB, blue: LSB


Updated time schedule

according to Progress Meeting 04.12.2007Nr. Work package/Milestone

1 SRON+DLR radiometric tests

2 Mechanic modifications

3 Electronic modifications

4 RAL integration

5 TM/TC test in Aire

6 Total system assembly and test

7 Antenna profile measurement

8 TV test

9 Flight rehearsal

10 Packing

11 Shipping

12 Flight preparation

13 Flight

14

15 All channels integrated and tested

16 Packing list ready

17 Travel to Teresina

18 End of Teresina Campaign

31.01.

31.03.

02.05.

15.06.

12.07 01.08 02.08 03.08 04.08 05.08 06.08 07.08 08.08


Time schedule• RAL and SRON integration and radiometric characterisation measurements

have to be coordinated

• Time requirement for RAL channel integration unknown

• Radiometric characterisation for RAL channel open

• Decision about additional TV test


Scientific capabilities of DLR 1.8 THz channelTransmittance, limb sounding 40 to 14 km, tropical. Water vmr 6.2 ppm @ 14 km, 4.0 ppm @15 km. Limb sounding barely feasible.

Transmittance, limb sounding 40 to 16 km, tropical. Water vmr 3.0 ppm @ 16 km, 2.9 ppm @17 km.

Polar conditions: 12 km barely


Species Line center/GHz LO range/GHz Sideband Preferred

OH 1834.75 1829.35-1830.25 USB X

OH 1834.75 1839.75-1840.20 LSB

OH 1837.8 1842.70-1842.20 LSB X

OH 1837.8 1833.50-1833.60 USB

H2O 1766.2 1770.70-1771.00 LSB

H2O 1880.75 1876.55-1875.65 USB X

H2O 1800.5 1805.65-1804.65 LSB

H218O 1815.85 1820.05-1820.85 LSB X

H218O 1815.85 1810.05-1811.65 USB

H217O 1783.4 1788.35-1788.80 LSB

H217O 1840.15 1844.20-1844.35 LSB

H217O 1840.15 1834.70-1836.00 USB X

HDO 1818.5 1823.70-1824.30 LSB

HDO 1818.5 1813.80-1814.30 USB

HDO 1853.9 1858.10-1859.60 LSB X

HDO 1853.9 1849.10-1849.70 USB


Species Line center/GHz LO range/GHz Sideband PreferredO18O 1875.04 1880.34-1880.74 LSB

O18O 1875.04 1870.04-1870.84 USB X

HO21805.5 1810.075-1810.125 LSB

HO21821.8 1826.45-1826.55 LSB

HO21821.8 1817.40-1817.70 USB X

HO21847.25 1842.68-1842.75 USB

CO 1841.36 1846.00-1846.10 LSB

CO 1841.36 1836.10-1836.56 USB XHCl 1873.40 1877.60-1878.40 LSB

HCl 1873.40 1868.15-1869.05 USB X


OH, 16 km tangent , white: DSB, blue: DSB-OH, green: USB, red: LSB


OH, 40 km tangent , white: DSB, blue: DSB-OH, green: USB, red: LSB


HDO, 16 km tangent , white: DSB, blue: DSB-H2O, green: USB, red: LSB


HDO, 40 km tangent , white: DSB, blue: DSB-H2O, green: USB, red: LSB


H217O, 16 km tangent , white: DSB, blue: DSB-H2O, green: USB, red: LSB


H217O, 40 km tangent , white: DSB, blue: DSB-H2O, green: USB, red: LSB


• Funding for integration of TELIS on HALO available for 2008/2009

• Since ASUR integration uncertain, TELIS would be valuable candidate for POLSTRACC demo mission

• TELIS integration in belly pod

• Limb sounding? Scientific benefit not explored

• Above flight altitude vertical resolution 5-10 km

• Remote sensing of clouds

• Temperature profiling like MTP

TELIS on HALO

telis progress meeting, oberpfaffenhofen, 3. december 2007 telis terahertz limb sounder

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