Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.naic.edu/alfa/ealfa/meeting1/talks/deshpande.pdf
Дата изменения: Mon May 8 22:43:32 2006
Дата индексирования: Sun Dec 23 01:56:35 2007
Кодировка:
Поисковые слова: п п п п п п п п п п п п п п п п п
NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA:
Radio Astronomy in the Multibeam Era
The ALFA Project
Avinash Deshpande

Senior Research Associate Radio Astronomy Group ALFA Scientific Coordinator


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

Arecibo L-Band Feed Array
Will revolutionize our ability to survey the sky Brings new observing paradigm to NAIC


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Front End
7 feed horns: 1 central + 6 on a ring stepped TE11 mode 25 cm diameter, 26 cm spacing Dewar rotation 200 degrees Polarization: dual linear (> 20 dB isolation) Bandwidth: 300 MHz (1225-1525 MHz) T(sys): 35 K (1.2 GHz) to 25 K (1.5 GHz) T(receiver): 8 K


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Front End
Beam size
Central: 230" X 201" Ave pixel: 231" X 204"

(cont)

Total coverage: 768" X 658" ~25th of a square degree

Gain
Central: 11 K/Jy Other pixels: 8.5 ­ 9 K/Jy


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Feedhorns and Location in Dome


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Front End Construction
Contract with Australia Telescope National Facility/CSIRO to design and fabricate front end NAIC effort includes: - antenna controls - IF/LO system - backend(s) - data acquisition and archiving


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Construction Schedule
Purchase order for front end: r 2002 Delivery at AO expected: Apr 2004 IF/LO system: p 2003 Backends (H/W & S/W): end of 2003 WAPPS (100 MHz): Ap

Se

4


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Schedule
-Apr 2004

(cont)

Pre-commissioning phase

Jan

Test of 7 copies from single pixel Commissioning/integration -Sep 2004 Tests/calibration Sep-Dec 2004 -In Apr


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

Project Management


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

Project Management

(cont)

Hardware Cost: $ 1,210,000 Front-end Contract Value ($US): $ 713,964 Effort: 10 technical & 6 scientific staff involved ~9 FTE person-years Software Requirements: Control and data acquisition software are NAIC responsibility Data-reduction software will be developed entirely by the respective consortia, and will be made available to the AO and users.


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

Project Management

(cont)

Post Commissioning: The ALFA system will be maintained by the NAIC and scheduled observing runs by the consortia would begin. The first runs will be treated as test and the ALFA technical team will provide active support to resolve remaining difficulties. The NAIC Director will have input from the ALAC and the DMC. Development on additional back-ends may continue through 2005. Full piggy-backing only begins when the additional backends become available.


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

Project Management

(cont)

Regular local technical meetings Monthly telecons with CSIRO ALFA Advisory Committee Altschuler & Giovanelli Data Management Committee Venkataraman & Cordes


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Advisory Committee
Advise NAIC Director on ALFA time allocation policies, survey progress review process, consortia guidelines, hardware needs, and other issues Members: Daniel Altschuler (NAIC/AO) co-chair Riccardo Giovanelli (Cornell) co-chair Miller Goss (NRAO), liaison to Visiting Committee Rich Kron (U Chicago/SDSS) Joel Weisberg (Carleton) + Co-chair of Data Management Committee + Avinash Deshpande (ex-officio)


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Science Consortia
Pulsar (37) - meeting held Nov 1-2, 2002 Extragalactic HI (51) - meeting set for March 15-17, 2003 Galactic HI and continuum (50) - meeting set for March 19-20, 2003 SETI interested in piggy-backing
(#): Number of prospective participants


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Pulsar Consortium
First meeting: Nov 1-2, 2002 37 attendees, international ALFA technical details by NAIC staff Survey parameters & strategies; time requirements Additional back-ends Data storage/porting; computing resources Post-processing (search) s/w; data products Follow-up observations Piggy-back surveys; prospects of parallel surveys Summary available on ALFA web page


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Pulsar Consortium

(cont)

Consortium organization (3 hr session) - Coordination committee (8 members) - Chair elected (Jim Cordes) - Point of contact at AO (Paulo Freire) - Subgroups to work on different issues (5) - Action items
Consortium report to NAIC (now available)


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA:
Radio Astronomy in the Multibeam Era
ALFA Surveys: A New Paradigm
Chris Salter

Senior Research Associate Head, Radio Astronomy Group Adjunct Professor of Astronomy


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA vs Single-Pixel Science
"Point & Shoot" at specific unresolved targets ­ Use the best available single-pixel system. "Survey" projects ­ ALFA is ~7 times faster than an L-band single-pixel system.

Surveying with ALFA
Example: Meridian scans at elevation slew rate (2.5 deg/min)
D e c (Zenith)

R.A.


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA Will Discover 1000 New Pulsars
Understand populations seen in radio and gamma ray bands Test notion that some pulsars are strange (quark) stars Exotic binaries

Pulsar-pulsar Pulsar-black hole
Test theories of binary evolution Test fundamental physics

Survey simulations by J. Cordes, D. Chernoff, and Z. Arzoumanian


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFALFA
All-Sky Fast ALFA Survey

Past surveys using Arecibo have given discrepant slopes for the faint end of the HI mass function, predicting number counts that differ by a factor of ten No other telescope can match Arecibo's sensitivity The best strategy is to survey a wide area of sky, but it is NOT necessary for this problem to integrate for more than about 5 sec/point


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFALFA:
A blind survey Even 1 sec integrations will detect thousands of galaxies ALFALFA will measure the faint end slope and may challenge models of the number and distribution of low mass halos nearby.

Survey simulations by R. Giovanelli


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

ALFA: Survey of Virgo Cluster
!Discovery of optically faint HI rich dwarfs !Probe of how gas content varies with local galaxy density !Study of apparent filamentary structure (elongation) of cluster itself


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

Recombination Lines

Continuu m

HI


NATIONAL ASTRONOMY AND IONOSPHERE CENTER

Piggyback ALFA survey
Deep pulsar search Deep ZOA HI survey Galactic plane HI SETI

A single survey providing data for multiple purposes will challenge hardware and software but optimize telescope usage.