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TELIS Science cases TErahertz LImb Sounder

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Title: TELIS Science cases TErahertz LImb Sounder


1
TELIS Science cases(TErahertz LImb Sounder)
  • Arno de Lange
  • Ruud Hoogeveen, Avri Selig
  • 3rd International Atmospheric Limb Workshop
  • MontrĂ©al, Canada
  • 25-28 April 2006

2
What is a Terahertz?
  • f 1 Terahertz 1012 Hz ? l 300 mm
  • 100-1000 THz (UV/Vis/IR) ? optics
  • 0.01 THz (10 GHz) ? electronics
  • Terahertz signals are hard to detect
  • Cannot directly be picked up by electronics
  • Optical detectors are blind for THz radiation
  • Detection recipe use radio techniques
  • Generate THz signal with well known
    characteristics
  • Mix atmospheric signal with generated signal ?
  • GHz difference frequency
  • Analyse difference frequency with conventional
    electronics

3
Why being interested in THz?
  • Very rich spectrum with well resolved lines
  • Almost no Rayleigh scattering (f 4)
  • Relative insensitive to PSCs, aerosols, cirrus
    clouds etc
  • Audience is this true?
  • Thermal emission spectrum ? not dependent on
    light source
  • What kind of transitions?
  • Electronic 1014 Hz (100 THz)
  • Vibrational 1013 Hz (10 THz)
  • Rotational 1012 Hz (1 THz)

4
500 650 GHz spectrum
5
Collaboration TELIS
  • 3 channels
  • DLR (GER) 1.8 THz
  • SRON (NL) 500 650 GHz (and THz)
  • RAL (UK) 500 GHz
  • Technology driven instrument
  • DLR Cryogenic 1.8 THz channel (OH measurements)
  • SRON Experience (HIFI) applied to EOS
  • RAL Miniaturisation
  • Platform
  • MIPAS-B stratospheric balloon gondola

6
Whats new?
  • 1991 UARS MLS (Microwave Limb Sounder)
  • 2001 ODIN/SMR
  • 2004 EOS MLS (including 1.8 THz channel)
  • TELIS in general
  • Cryogenic temperatures ? 10x better S/N ratio
  • DAC (Digital Auto Correlator) 2x2 GHz bandwidth
    (_at_ 2 MHz)
  • Overlapping and complementary with MIPAS-B
  • SRON channel
  • Low noise amplifier, SIS mixer etc.
  • Solid state local oscillator
  • SIR (Superconducting Integrated Receiver) ?
    miniaturisation

7
Superconducting Integrated Receiver (SIR chip)
8
SIR channel
9
SIR channel
10
SIR channel
11
SIR channel First light
12
SIR channel OCS spectrum
p 0.23 mbar l 0.50 m LO 625.550 GHz
13
Specifications (SIR channel)
  • Vertical resolution 1.5 km
  • Intensity accuracy 0.2 K _at_ 1 sec integration
    time
  • Noise temperature 200 300 K
  • Altitude range tropopause platform height (35
    km)
  • Frequency range 500 650 GHz
  • Single scan 2 GHz (or 2 x 2 GHz) TUNABLE!!
  • Frequency resolution 2 MHz
  • Species H2O, O3, O2 rare isotopes
  • HCl, ClO, HOCl
  • N2O, NO, NO2, HNO3, HCN
  • CO, H2CO, OCS
  • H2O2

14
Planned flights MIPAS-B with TELIS
  • Qualification flight
  • April 2007 Kiruna (Sweden)
  • Science flight
  • Fall 2007 Terasina (Brazil)

15
What to measure?
  • Species by SIR channel
  • HCl, ClO, HOCl
  • (BrO, HBr)
  • H2O, O3, O2, (H2O2, HO2)
  • NO, N2O, NO2, HNO3
  • CO, H2CO, HCN
  • OCS, (SO2)
  • isotopes H2O, O3, O2
  • Science cases pertain to
  • Ensemble measurements
  • Isotope measurements

16
Science cases
  • Ozone chemistry
  • Stratospheric water
  • UTLS transport
  • NAT and HNO3

17
I. Ozone chemistry
HCl ClONO2 ? HNO3 Cl2 ClONO2 H2O ? HNO3
HOCl
18
II. Stratospheric water
  • Central questions
  • What is the origin of stratospheric water?
  • Does the amount of stratospheric water increase?
  • If so, why?
  • Importance to ozone chemistry
  • More stratospheric water more PSCs more
    active Cl
  • O(1D) H2O ? 2 OH more O3 depletion by HOx
    cycle

19
How to get insight?
  • By water isotopes
  • All physical and chemical processes have
    different signatures for different isotopes
  • Measuring enrichment/depletion gives insight in
    the different processes
  • By water and a passive tracer (CO, N2O)
  • UTLS transport

20
Information by water isotopes
  • HDO
  • Largest enrichment/depletion (up to -900)
  • Good tracer for UTLS water transport
  • H217O en H218O
  • Measuring both gives insight in chemistry
  • Questions
  • Is the amount of stratospheric water dependent on
    the temperature of the tropopause?
  • Is there an isotope effect with altitude?
  • Is there more enrichment in the tropics?

21
H2O isotope spectrum
22
H2O isotope spectrum (THz channel)
23
III. H2O, CO/O3, and/or N2O/O3
  • H2O
  • Water flux UT ? LS
  • CO, N2O
  • Total flux UT ? LS
  • CO/O3 and/or N2O/O3
  • Age of air
  • Questions
  • When and where comes air (including water) from
    UT in LS?
  • How does the water concentration change
  • as a function of (tropopause) temperature?
  • as function of total air flux?

24
IV. PSCs
  • Type 1 PSC NAT particles (HNO3.3H2O)
  • PSC composition, formation mechanism, and ozone
    depletion processes not entirely understood

25
HNO3 and NAT
  • Formation/composition
  • HNO3(g) and NAT simultaneous measurements
  • NO/NO2 ratio ? insight in nitrogen cycle and PSCs
  • OH/HO2 ratio ? insight in hydrogen cycle and PSCs
  • HNO3, NO/NO2, and OH/HO2
  • denitrification of lower stratosphere
  • dehydration of lower stratosphere
  • Is there also NAT above the tropics?
  • Coldest place tropical tropopause

26
Conclusion
  • TELIS is a sub-mm instrument with excellent
    specifications
  • 3 channels
  • MIPAS-B balloon
  • Qualification flight April 2007
  • Promising science cases
  • Ozone chemistry
  • Stratospheric water
  • UTLS transport
  • NAT and HNO3

27
Ozone isotope anomaly
  • Mass dependent fractionation
  • Enrichment/depletion of 17O en 18O in fixed ratio
  • World wide
  • In all kind of materials (water, minerals, ice)
  • Main exception
  • Atmospheric ozone
  • Origin is not entirely clear, but
  • O O2 ? O3
  • Reaction rate for rare isotopes (w.r.t. 16O3)
    0.90 1.53

28
Ozone anomaly as chemistry tracer
  • If something reacts with ozone
  • the anomaly will (may) be transferred.
  • Oxygen isotope measurements are a tracer for
    ozone chemistry.
  • H2O and O3 isotopes ? HOx chemistry
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