Terahertz Limb Sounder TELIS. Axel Murk M. Birk, R. Hoogeveen, P. Yagoubov, B. Ellison

Transcription

1 Terahertz Limb Sounder TELIS Axel Murk M. Birk, R. Hoogeveen, P. Yagoubov, B. Ellison

2 Overview THz Limbsounder with three cryogenic receivers: 1.8 THz HEB mixer with solid state LO (DLR) GHz superconducting integrated receiver (SRON) 500 GHz compact SIS receiver with dichroic SSB filter (RAL) Balloon-borne observations together with FTIR-Instrument MIPAS-B (IMK) Tight mass, size and power constraints (<70kg, <150W)

3 MIPAS + TELIS Gondola

4 Scientific Goals Complete chemistry mission with MIPAS-B, special focus on short-lived species in stratosphere + lower stratosphere Additional advantage of combined payload: cross validation of several species Validation of satellite instruments NLTE assessment of CO and NO with MIPAS-B Development of new sensitive sensor technologies for space applications

5 TELIS Species DLR GHz: OH, HO 2, HCl, HOCl,NO, NO 2, O 3, H 2 O, O 2, RAL GHz:: BrO, ClO, O 3, N 2 O,... SRON GHz: BrO, HO 2, H 2 18 O, H 2 17 O, HDO, ClO, HCl,, HOCl, O 3, H 2 O, NO, N 2 O, HNO 3, CH 3 Cl, HCN Additional nadir view for water profiling + cloud physics TELIS highlights Sensitivity improved vs. MIPAS-B MIPAS-B species Ozone relevant: O 3, NO, NO 2, HNO 3, HNO 4, N 2 O 5, ClONO 2, ClO, HOCl, ClONO 2 Water isotopomers: HDO, H 16 2 O, H 17 2 O, H 18 2 O Tracers: N 2 O, CH 4, CO, SF 6, CF 4, CCl 4, CFC-11, CFC-12, CFC-113, CH 3 Cl,... Short-lived source gases: NH 3, acetone, PAN NMHCs:C 2 H 6, C 2 H 2 Species involved in cloud physics: H 2 O, HNO 3, NH 3, OCS,... Cirrus cloud parameters: extinction, volume, composition, size distribution Species measured with MIPAS and TELIS

6 Specifications Radiometric T sys : < 600 K (RAL) < 400 K (SRON) < 6000 K (DLR) Gain error: < 1% Offset error: Baseline ripple: Spectral < 1 K < 0.1 K Omnisys Autocorrelator with 4 GHz bandwidth Resolution: < 4 MHz Bandwidth: 2 GHz (SRON, DLR) 4 GHz (RAL) Pointing Altitude resolution < 2 km Pointing accuracy: < 3 (500 m) Channel coincidence: < 3 (500 m) Pointing offset: from retrieval of O 3, O 2, accuracy < 1

7 Schematic Overview

8 TELIS Subystems Calibration Unit 6 kg Pointing System 9 kg Transfer Optics 7 kg Frame 11 kg Cryostat 25 kg + cold optics Mass: 58 kg + Cold optics IF Autokorrelator Cables Heat pipes Electronics Batteries Radiation Plate

9 Transfer Optics Beam Path DLR Beam Path RAL Polarizer Radiation from BB Unit Dichroic Beam Path SRON

10 THz Channel (DLR) Diplexer HEB Mixer SSB Filter Local oscillator

11 500 GHz Channel (RAL)

12 500 GHz Channel (RAL) Optics + Dichroic LO SIS HEMT

13 GHz SIR (SRON) Superconducting Integrated Receiver (SIR) by IREE, Moscow SIS Mixer with Lens Antenna Feed, Flux-Flow Oscillator and harmonic mixer for PLL on one chip

14 Complete SIR Receiver SIR in Magnetic Shield SSB Filter (MPI) RF Input Harmonic generator for PLL

15 SIR Hardware and T Sys Noise temperature of a SIR Prototype. Tuning will be optimized for flight model.

16 Conical Calibration Target Red: ESA CHL (MARSCHALS, B-SMILES) Black: Smaller version for TELIS Thomas Keating Ltd., UK

17 Reflectivity of the TELIS CHL Measurements at 625 GHz with quasi-optical reflectometer and Abmm vector network analyzer Sliding load calibration with translation stage Backscatter below 70 db

18 Antenna Simulations Optical Design based on Gaussian Beam Analysis Statistical Tolerancing Analysis with ZEMAX Physical Optics Simulations with GRASP Simulation of the complete transfer optics Effect of the lens antenna feeds of SIR and THz channel Tolerancing for the most critical elements (very slow) Random surface errors of the telescope Deformation of the primary reflector modeled with Zernike-Modes

19 GRASP Simulations: Telescope

20 Complete THz Optics + Lens Feed

21 Telescope Misalignment THz channel

22 Random Surface Errors of Primary Assumed peak errors: 1 µm, 5 µm, 10 µm ( 0.47 for rms error) Assumed length scales: 10 mm and 5 mm

23 Simulations with Random Errors THz channel

24 Antenna Measurement Program Mechanical probing of the reflectors Optical alignment with lasers Single reflector compact range measurements with thermal line source for all channels (similar setup as H. Pickett, JPL) Compensated compact range (FH München) at 500 and 625 GHz Planar nearfield measurements of the telescope with ABmm vector analyzer Test of the nearfield setup with parabolic reflector at 210 GHz GRASP simulation including Potter horn of transmitter Scattering at the edges Multiple scattering from base plate Flat edges

25 Nearfield Results at 210 GHz P. Fürholz, Universität Bern

26 Project Status and Schedule Prototypes of THz and SIR channel ready and tested Problem areas: final THz LO and HEB mixer not yet delivered, SIR only with limited tunability, delays with 500 GHz channel Autocorrelator, IF stages and calibration target: Delivered and tested Transfer optics, telescope and frame ready by Dec. 2005, cryostat currently in production First TELIS/MIPAS flight in summer 2006 Proposal for utilization of HALO aircraft after 2008