pass – a permanent all sky survey for the detection of transiting planets

©Hans Deeg, Nice 05/2004

PASS – a Permanent All Sky Survey for the Detection of Transiting Planets

•an instrument capable to perform a permanent photometric survey of the entire (visible) sky

•principal objective: detection of all giant planets that are transiting bright stars

•many additional objectives can be realized-Detection/study of variable phenomena of all kinds

•prototype of PASS at Obs. Teide, Tenerife

•possiblities for collaborations - placement on Dome C ?

Hans J. Deeg1, Roi Alonso1, Juan Antonio Belmonte1, Khalid Alsubai2, Laurance Doyle3

1Instituto de Astrofísica de Canarias, Spain, 2Univ of St Andrews, Great Britain, 3SETI Institute, USA


Detection of giant planet transits of all stars, with a magnitude limit of V ~ 10.5.

•Surveying about 150 000 stars in one hemisphere, 250 000 in entire sky

• ~60 planets may be detected in one hemisphere, 100 in total.

This will give the best sample of planets for follow-up studies:

• detects star-planet systems with highest brightness (=signal), typically nearby

ones.

• follow-up measurements need highest possible S/N for scientific advances

(i.e. spectroscopy of atmosphere, multi-color photometry) .

• transiting planets detected by PASS will provide an optimum sample for a

variety of research (using larger ground based or space based instruments) to

gain a deeper insight into the formation and current physical status of giant

planets and their atmospheres.

Main-Objective of PASS:


E W

S

NLocal Sky view28.5°N

current working hypothesis:•15 cameras on fixed mount •f=50mm, 1k x 1k or 2k x 2k CCDs•28°x28° field of view (50 or 100”/pix)•complete coverage for altitudes > 34°•coverage > –17.5° from Tenerife•full sky coverage with 2nd instrument in South

horizon

dashed line: 30°alt

The Instrument


PASS would perform real-time all-sky observations for transit detection.

planet transit detection experiments

real-time all-sky-observations

PASS

telescopes with guiding:surveying small zones in sky

fish-eye lenses:for meterological surveys,observing site quality,meteorite detection

The context of other experiments:


Anxilliary Objectives of PASS:

Detection of any temporal astronomical phenomena:•Detection and follow-up of stellar variabilities with low amplitudes (up to 0.1%, depending on stellar brightness and frequency)

-variable stars of any kind-flares

•Detection of supernovae•Recording of frequency and direction of meteorites•Detection of optical counterparts to gamma ray bursts and ‘optical flashes’•Detection of asteroids, comets, stellar occultations (e.g. by Kuiper-belt objects)

Sky-quality and meteorological statistics:•Recording of sky brightness and extinction in all directions•Percentage of clear sky, clouds•Detection of satellites and airplanes (intrusions into protected sky area over observatory)

long-term follow-up ofeclipsing binary minimum times isanother method to detect planets


The PASS Instrument

Features:

•permanent survey of entire visible sky is only possible with a fixed instrumment

•mechanical simplicity, low maintenance

•Stars will trail over exactly the same pixels every night at the same sidereal time:

no guiding or flatfielding errors, high stability and repeatability.

•brightness-behaviour of each star can be compared across many nights and against many other stars.

•Long duration of observations allows calibration for different meteorological conditions (eg. extinction, temperature). Seeing is not important.

N

1m

Working hypothesis:•15 Cameras on a common fixed mount.• f=50mm lenses, 28°x28°f.o.v.•CCD detectors with about 25x25mm size (1k x 1k CCD: scale of 100”/pix.)

drawn with 10 cameras only


Yearly observational coverage (instruments in N and S)

Assumptions:-one site at 30ºN -one site at 35ºS- complete sky above 30º altitude is observed-1500 hrs/yr of clear sky

blue line: coverage from Nviolet line: coverage from Sgreen line: summed coverage

(night-hours may not overlap in N and S)with sites in Europe and (Chile or Australia, Antarctica):-> fairly uniform coverage over entiredeclination rangeExpected number of hours that a star at a given declination

can be observed in one year

0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

1600.0

-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90declination

yearly coverage (hours)

N +30°S -35°Sum (N+S)


Dome C yearly observational coverage

Assumptions:-one site at 30ºN -Dome C at 75ºS- complete sky above 15º in Dome C-2000 hrs/yr in Dome C-1500 hrs/yr in N

blue line: coverage from Nviolet line: coverage from Sgreen line: summed coverage

Expected number of hours that a star at a given declination can be observed in one year

0.0

200.0

400.0

600.0

800.0

1000.0

1200.0

1400.0

1600.0

1800.0

2000.0

-90 -75 -60 -45 -30 -15 0 15 30 45 60 75 90declination

yearly coverage (hours)

N +30°Dome CSum (N+S)


Approach of feasability study

1. Theoretical S/N calculations

2. Photometry on artificial images with all known noise characteristics

3. Photometry on real images under controlled conditions

agrees well

TBD

financed by Span. Plan Nacional Astronomía y Astrofísica


S/N calculationsS/N from photometry onsimulated images, texp=20s

90 x90 pix,2.5° x 2.5°10° gal. lat.

Curve is Total S/N in 20 secfrom left gaph

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

3 4 5 6 7 8 9 10 11 12 13Stellar Brightness (mag)

mag err

photonbackgrdscintillationreadnoisedigital. noisedark noisetotal,texp=20stotal in 900stra.det. limit

Limit for transit detc:rms ~3.5mmag in 900sec

PASS - Baseline :CCD KAF1001 (1k x1k)50mm, f/2.0, texp=20sec, obsv. site: alt=2400m, no moon, 1.4 airmass


The PASS prototype

Started this year with funding by Span. Science Ministry. (Pl. Nac. AYA-2002-04566 )

- 1-2 cameras; currently a loaned AP10, 2k x 2k Thomson CCD, further one will be obtained soon.

- lenses Nikon 50mm/1.2, 50/1.4- fixed mount with adjustable tripode

head.- Sequences of a few hours have been

taken, analysis in progress- Construction of dome in progress- Potential placement at DomeC

no moving part with Kodak KAI series interline CCD

‘First light’ 16 Jan 04with AP10 (2k x2k) camera

loaned by Univ. St.Andrews (K. Horne)


Objectives of PASS prototype• get observational data for

feasibility study of PASS concept

• detailed characterization of instrument in its capability to detect planets (’discovery space’)

• development of photometry software

• comparison with simulated data

• study about possible additional objectives

• define specifications for a final instrument

• start of planet survey with 2–camera system


PASS0 imagetexp=60sec, f/2.0 (f=50mm)

stars to ~11 mag can be identified visually

seq. of 20 sec exposurestaken in first night


Collaborations are seeked...

• real time pipeline processing among several computers

• everything related with databases

• definition of stellar sample (all-sky study on MS fraction; stellar types)

• classification / interpretation of variables’ lightcurves

• any kind of study towards definition of auxiliary objectives

• follow-up/verification observations of candidates (transits and variables/aux. objectives)


Conclusions

An instrument with a novel design for planetary transit detection is being developed

•Primary goal is detection of ALL giant-planet transits around bright (nearby) stars

•Ample range of auxilliary objectives

•Realization of these objectives needs a variety of expertise and development of analysis modules, opportunities for participation

• Observations with prototypes 2004-05:-detailed characterization of instrument capabilities-verification of achievability of objectives (‘detection-space’) will result

•Interested in collaborations

•more info in www.iac.es/proyectos/pass; paper accepted for PASP

http://www.iac.es/proyectos/pass





pass – a permanent all sky survey for the detection of transiting planets

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