The Digital Revolution

in Wide-Field Imaging:

Electronic detectors(CCDs) developed in the’70s and 80’s completelyrevolutionized many areasof astronomy. The earlydetectors, however, weretoo small for wide-fieldimaging, and this field fellinto decline.Recently the situation haschanged and the cost ofCCDs has fallendramatically. Cameraswith up to 100M pixelshave been deployed on anumber of largetelescopes, and aregenerating images ofhuge coverage and depth.The Pan-STARRS projectwill further this advance.It will generate digitalimages of the whole skywith unparalleledsensitivity and imagequality. These will beused to attack scienceobjectives ranging fromthe solar system tocosmology.

Rolf-Peter Kudritzki

IfA Director

Nick KaiserAstronomer

Institute for Astronomy2680 Woodlawn DriveHonolulu, HI 96822-1897(808)956-8566 (phone)(808)956-4644 (fax)

www.ifa.hawaii.edu

Pan-STARRS: A Panoramic Optical Imager

The Pan-STARRS System is adedicated wide-field imager featuring

• an array of small telescopes, butwith very wide field of view

• huge CCD cameras with 109 pixelstaking images every 90 seconds

• state-of-the-art data processingpipeline and interface to the Na-tional Virtual Observatory

• unique time resolution capability al-lowing detection of variable or mov-ing objects, as well as deep imagesof the static sky

• more power than all existing imag-ing telescopes combined

The use of small telescopes offers sev-eral advantages:

• low cost

• rapid construction timescale

• diversity of operation modes

• simple optical design

• low environmental impact

4 Pan-STARRS is an array of 4 small tele-

scopes. These may be housed within one of

the existing UH facilities. CCD cameras with

109 pixels mounted on each telescope can take

images every 90 seconds, generating ∼ 3 ter-

abytes per night of operation.

The Science:

• Pan-STARRS can survey the visiblesky in 4 nights. This unique time-resolution capability will enable itto find ‘killer asteroids’, supernovaeand other transient objects.

• Pan-STARRS will also generate avery deep ‘digital atlas’ of 70% ofthe sky and ultra-deep images ofselected regions

• These data will open up a new di-mension in studies of the solar sys-tem and our galaxy. They will alsoaddress fundamental questions incosmology such as the nature of thedark matter and the ultimate fateof the Universe.

Survey Strategies

Asteroid SearchesCollisions with asteroids present a significant threatto humanity. A 300m asteroid impact in the Pa-cific would wipe out all seaboard cities. Detectingall dangerous objects is a high priority for astronomyin the coming decade. However, the task is challeng-ing since the objects are faint and moving, requiringshort exposures and scanning very large areas of sky.The design is ideally suited to this task

• Pan-STARRS can reach 24th magnitude in 60s,allowing it to detect 300m size asteroids.

• The 4-telescope design allows very efficient detec-tion of moving objects.

• it can cover 3,000 square degrees of sky per night.

• it will scan 10,000 square degrees three times in 2weeks, allowing multiple detecting of moving ob-jects and orbit determination.

• The survey will cover 70% of sky (28,000 squaredegrees) and detect nearly all dangerous objects.

The repeated short exposures and full sky cover-age open up a huge potential for discovery of tran-sient objects (supernovae, gamma-ray bursts etc)and as yet unknown phenomena.

The huge numbers of supernovae detected andmonitored by this program will provide a precise mea-surement of the expansion history of the Universe,and will nail down the properties of the mysterious‘dark energy’.

All Sky SurveyStacking the survey scans will give very deep cu-mulative images of the full sky. This multi-colorall-sky survey will result in a unique data-base andwill outperform all current surveys by a large mar-gin. The resulting images and catalogs of objectswill find many applications in galactic studies and incosmology.

Ultra-Deep SurveyRoughly 1/3 of the observing time will be devoted

to ultra-deep imaging of a number of selected fields.This will allow detection of galaxies, quasars,

stars to very faint magnitudes. One key applica-tion of these data will be mapping the distributionof dark matter in the Universe through the gravita-tional lensing effect. Such a dark-mass inventory willbe invaluable for testing theoretical models for theformation of structure in the Universe.

The Computing Challenge

Pan-STARRS will generate 4×109 pixel images every90 seconds; this amounts to '3 terabytes per night.Moreover, real-time processing is required to detecttransients and moving objects.

The accumulated images also present a challenge:The 28,000 square degrees in 3 passbands results ina '100 terabyte database.

Maintaining this database is a non-trivial problem,and an even greater challenge is in the developmentof software to allow the extraction of science fromthis repository.The goals are to:

• allow the community (scientific and public) to in-terrogate the database

• build on the experience in the scientific communityfrom other surveys

• interface to the National Virtual Observatory — amajor astronomical software initiative

The Site

The 4 Pan-STARRS telescopes are very small com-pared to modern large telescopes, so the environ-mental and cultural impact is less. Indeed, one con-cept being explored is to house the entire facilitywithin the existing UH 2.2m telescope building.

Other possibilities are being considered, includingHaleakala.