SECCHI Consortium Meeting, Paris - March 2007 Heliospheric Imagers – Instrument Status Chris Eyles Space Science & Technology Department (RAL) Richard Harrison, Chris Davis, Danielle Bewsher, Steve Crothers and Jackie Davies (RAL) Jean-Philippe Halain (Centre Spatiale de Liege) Dan Moses and Jeff Newmark (Naval Research Laboratory)

Chris Eyles Space Science & Technology Department HI Design Requirements Geometrical requirements: –To view the Sun-Earth line with unbroken coverage from Corona to Earth orbit –Opening angle of 45º governed by average CME width over equator Brightness levels: –Need to achieve rejection to < 3x and < B/Bo to detect CME signal –Have to contend with contributions from the F-Corona, planets, stars, the Earth and Moon

Chris Eyles Space Science & Technology Department HI Specifications HI-1HI-2 Direction of centre of FOV13.98º53.68º Angular field of view20º70º Angular range3.98º – 23.98º18.68º – 88.68º CCD pixel size35 arcsec2 arcmin Image array (2x2 binning)1024x1024 Image bin size70 arcsec4 arcmin Spectral bandpass nm nm Nominal exposure time12-20 s60-90 s Nominal exposures per image7050 Nominal image cadence60 min120 min Brightness sensitivity (B o = solar disk)3 x B o 3 x B o Straylight rejection (outer edge)3 x B o B o

Chris Eyles Space Science & Technology Department Early Mission Summary (1) Launched on 25 Oct 2006 –Decontamination Heaters switched on few hours later SECCHI Electronics and HI Cameras switched on 27 Oct –Electronics checks, dark images, Cal LED images Outgassing until 22 Nov –Decontamination Heaters switched off –CCD cooling curves and dark charge measurements (see later) –Cal LED and dark images HI-A Door deployment and first light on 13 Dec First Lunar swing-by and heliospheric insertion of STEREO-A on 15 Dec –HI-2A images of Moon !!!

Chris Eyles Space Science & Technology Department HI-A First Lights

Chris Eyles Space Science & Technology Department HI-A Lunar Swingby

Chris Eyles Space Science & Technology Department Early Mission Summary (2) HI-B Door deployment and first light on 11 Jan –HI-1B images of Comet McNaught !!! Second Lunar swing-by and heliospheric insertion of STEREO-B on 21 Jan A reduced synoptic observing programme began late-Dec (for HI-A) –Summed sequences of 25 x 24 sec exposures for HI-1 and 50 x 50 sec exposures for HI-2, both every 2 hours –Interspersed with various calibration activities, including S/C off-points and rolls Various calibration and commissioning activities over period Dec – date –HI straylight off-point calibrations (see later) –SCIP stepped calibration rolls –Open Door exposure time linearity sequences –Open Door Cal LED images (LED + sky; sky only)

Chris Eyles Space Science & Technology Department Comet McNaught (HI-1A Jan 2007)

Chris Eyles Space Science & Technology Department SCIP-B Stepped Calibration Roll

Chris Eyles Space Science & Technology Department Early Mission Summary (3) Just starting routine synoptic observing programme (see later) HI-A/B calibration rolls planned for 13 and 15 Mar –90/270 deg simultaneous rolls; spacecraft are rolled so that HI-A and HI-B view same area of sky to North and South of ecliptic –180 deg rolls; each spacecraft in turn rolled so that HI-A and HI-B view same area of sky centred on ecliptic

Chris Eyles Space Science & Technology Department HI CCD Cooling and Dark Charge Dark Charge (DN/pixel/sec) HI-1AHI-2AHI-1BHI-2Be2v value* +20ºC ºC Fitted dark charge vs T relationship - I dark = A T  3 exp(  6400/T) (T in deg K) * Based on e  /pixel/sec and 1 DN = 15 e 

Chris Eyles Space Science & Technology Department HI Thermal Status HI-AHI-B Structure-70 to -23ºC-68 to -29ºC S/C Interface-1ºC0ºC0ºC HI-1 CCD-83ºC-80ºC HI-2 CCD-80ºC-76ºC HI-1 Lens Barrel-15ºC-29ºC HI-2 Lens Barrel-15ºC CEB Internal-13ºC Wax Actuator-72ºC-71ºC All temperatures are well within operating limits HI-1B Lens Barrels stabilized at -29ºC with Operational Bus Heater CCD temperatures are very satisfactory

Chris Eyles Space Science & Technology Department HI-A Straylight Off-Point Calibration (HI-1) Spacecraft off-pointed in steps in HI pitch: –0.25º, 0.5º, 0.75º, 1.0º and 1.5º towards Sun –0.5º and 1.0º away from Sun Stars removed with median filter, then measured F-corona intensity at a number of points across centre-line of FOV Values plotted against angle from Sun centre allowing for off-point R  n profile fitted to nominal pointing values 1 DN/sec ~ 1.2 x B/B O for HI-1 –Straylight rejection better than 2 x B/B O over most of FOV Margin of at least 0.5º in off-pointing from Sun

Chris Eyles Space Science & Technology Department HI-A Straylight Off-Point Calibration (HI-2) R  n profile fitted to nominal pointing values –Value of n is very different for HI-1 and HI-2, 2.38 and 1.85 respectively, difference in spectral response? 1 DN/sec ~ 2 x B/B O for HI-2 –Straylight rejection better than 2 x B/B O over most of FOV Margin of at least 0.5º in off-pointing from Sun

Chris Eyles Space Science & Technology Department Synoptic Observing Programme (1) HI-1HI-2 Exposure Time24 sec50 sec Exposure Cadence30 sec60 sec Number of Images in Summed Sequence5099 Duration of Exposure Sequence25 min99 min Summed Sequence Cadence40 min2 hr Observing Duty Cycle50%67% In addition take full-resolution single images at regular intervals –One every 2 days for HI-1 –One every 4 days for HI-2

Chris Eyles Space Science & Technology Department Synoptic Observing Programme (2) Exposure times selected on dynamic range considerations –24 sec exposure for HI-1 gives maximum F-corona signal ~ 60% of dynamic range; very few saturated stars in HI-1 (~ 0 – 1) –50 sec exposure for HI-2 gives ~ 3 – 6 saturated stars Exposures at multiples of 30 sec simplifies scheduling Duration of exposure sequence results in drift of stars by ~ 1 bin –Minimal smearing of star images Summed sequence cadences constrained by telemetry allocation but matched to respective plate scales and typical velocity of coronal ejecta

Chris Eyles Space Science & Technology Department HI Instrument Health and Status The HI instruments are performing superbly HI CEB and other electronics performance entirely nominal Thermal performance nominal –All temperatures within operating temperature limits –CCDs operating at ~ -80ºC; dark charge negligible, high tolerance against radiation damage effects No new issues or problems since launch Calibrations of flat fields, pointing offsets, etc proceeding well

Chris Eyles Space Science & Technology Department HI Instrument Issues Three issues were known about pre-launch: Thermal leak in HI-1B Lens Barrel –Very minor, requires operating set-point of HI-1B Optics to be -29ºC rather than -15ºC –No impact on performance whatsoever Off-axis PSRF of HI-2B inferior to HI-2A –Also minor, issue was found late in programme –No significant impact on Level 1 science; star removal from images will be more challenging Bright Earth in HI-B –Issue arises from fundamental orbital mechanics and the consequent (and inevitable) mission design. –Dynamic range of cameras is excellent

Chris Eyles Space Science & Technology Department First solutions from fitting to star-fields show plate-scales, distortion parameters, etc consistent with pre-launch values PSFs consistent with pre-launch values Values in pixels – Tests during AIV showed that HI-2B PSF problem is not a simple focus setting error –No significant impact on Level 1 science –Star subtraction more challenging; stellar photometry may be somewhat compromised –Images not so photogenic HI Imaging Performance Pre-Launch PSFOn-Orbit PSF FWHMHEWFWHM est HI-1A3 – 4 ~ 3 – 4 HI-2A3 – 6 ~ 3 – 8 HI-1B3 – 4 ~ 3 – 4 HI-2B3 – 103 – 12~ 3 – 12

Chris Eyles Space Science & Technology Department HI-B Bright Earth Issues (HI-1) Earth first produced significant stray light effect on HI-1B on day 98 (Jan 30) –Sun-Earth angle was 34.5º Earth will leave HI-1B FOV (Sun-Earth angle 24º) around day 150 (Mar 23) Sun-Earth angle will return to 34.5º around day 169 (Apr 11) –Guarantees that Earth will cease to be an issue for HI-1B by mid-Apr –In fact will be significantly earlier because Earth irradiance is more than an order of magnitude lower than on day 98 A recent HI-1B image (25 Feb): Surface brightness < 10% of F-corona locally

Chris Eyles Space Science & Technology Department HI-B Bright Earth Issues (HI-2) Earth signal is ~ 5 x photoelectrons per pixel (in 10 sec) –~ 2.5 x 10 5 x CCD full-well depth!!! –Also ~ 2.5 x 10 5 x system dynamic range By mid-June Earth irradiance will be order of magnitude lower –Spacecraft separation still only 13º –Success of on-going modeling and background subtraction studies will determine how much earlier Earth will cease to be an issue. HI-2B image (10 sec exposure) from 6 Feb: Surface brightness < 10% of F-corona locally

Chris Eyles Space Science & Technology Department The Lunar Transit in HI-B 19 Feb UT (full-res image) 28 Feb UT (full-res image)

Chris Eyles Space Science & Technology Department HI Instrument Status Conclusions The performance of the instruments is excellent No new issues or problems since launch The Bright Earth will cease to be an issue for HI-1B by mid-April or earlier and for HI-2B by mid-June or earlier Excellent progress with calibrations –First flat-fielding results –First star-field fitting results –Pointing information being implemented in FITS headers (CRPIX, CRVAL, PCj_i, PV2_1, initially with nominal off-points, soon with updated values from star fields) HI is well placed for start of mission science phase