1. CAVIAR science meeting, NPL 2 nd June 2008 Page 1 Update on instrument upgrade and calibration planning Paul Green, Alan Last, Ralph Beeby, Juliet Pickering and John Harries Imperial College London

2. CAVIAR science meeting, NPL 2 nd June 2008 Page 2 The TAFTS Instrument dual-input Martin-Puplett (polarizing) FTS with two spectral bands measure both nadir and zenith (+net) 4 liquid helium cooled detectors –80-300cm -1 (2 x Ge:Ga) –300-700cm -1 (2 x Si:Sb) resolution: 0.12cm -1 (apodized) single scan: 2 secs 4 internal BB sources employs Brault sampling scheme all built in-house (J Murray + A Canas) UKMO C-130, ARA Egrett, BAe-146

3. CAVIAR science meeting, NPL 2 nd June 2008 Page 3 Introduction Upgrade progress –Beamsplitter –Scan mechanism –Optics –POB / Calibration BBs NPL calibration planning

4. CAVIAR science meeting, NPL 2 nd June 2008 Page 4 Beamsplitters New polarising beam splitters from Cardiff, Improved performance: –Finer grid, improved high wavenumber performance. –Thicker, polypropylene substrate giving reduced absorption features and improved vibration characteristics. –Sandwich construction for amplitude/polariser alignment –Caveats: Untested in these specific circumstances, polypropylene known to stretch in prolonged vacuum. Amp BS orders, narrowed. Substrate thickness needs tuning. Peter Ade’s group at Cardiff Uni are currently working hard on technical aspects, but delivery date has slipped. Unavailable for 2008 campaign, look to install for 2009.

5. CAVIAR science meeting, NPL 2 nd June 2008 Page 5 Scan mechanism linear motor Parker Automation MX80L found to be problematic with current cabling configuration. Initial malfunction in Jan 2008, but still had reliability issues in April. Renovate the existing system. –Realign carriage –New drive cord material with pre-tensioning –Electronics –New laser Testing has gone well. Reliable scan in lab.

6. CAVIAR science meeting, NPL 2 nd June 2008 Page 6 Other renovations Optics –New HeNe laser installed. –New windows and mirrors throughout. –New rooftop for 2009 calibration and flight campaigns. Calibration sources –New higher precision PRTs and measurements electronics calibration completed. Progress with calibration routine –Optical model of instrument well developed.

7. CAVIAR science meeting, NPL 2 nd June 2008 Page 7 NPL calibration planning NPL site visit 28 th March –NPLxBB fitting, lab space, access, LN2 dewars, use of ICxBB etc. –Have initial calibration plan, will firm up over next month. NPL calibration in late June/early July. Analysis resultant dataset before flights in August.

8. CAVIAR science meeting, NPL 2 nd June 2008 Page 8 Closing Remarks Have encountered a couple of set backs. Renovated scan mechanism working well. NPL calibration starts on 30 th June. A test flight [alongside ARIES] in mid-August. Flight campaign 13 th Aug – 25 th Sept. Revisit scan motor replacement, worm drives, for instance, for 2009 campaign.