THE FUTURE OF THE ARECIBO 305 m TELESCOPE

Don Campbell

NAIC/NRAO Single Dish Summer SchoolJuly 17, 2009

The keys to success for any organization:

• A first class “product”

• The willingness/ability to innovate

If these conditions are met the “customers” will come.

How does this apply to the Arecibo 305 m telescope?

Telescope is old but a great “product” combined with a long history of innovative improvements to the telescope and its instrumentation that has kept it at the forefront of research in astronomy and atmospheric sciences.

1963Primary objective – Incoherent scatter radar measurements of ionospheric parameters – electron density, temperatures, winds, composition as function of altitude

Made steerable spherical antenna to allow:

Radar studies of terrestrial planets and the Moon

Radio astronomy

Characteristics:Maximum frequency 600 MHz - set by the accuracy of the mesh surface

Expected lifetime ~ 10 years BUT

Structure of telescope very well designed and constructed

Telescope completed in 1963

Major achievements in radio and radar astronomy 1963 - 1973:

Measurement of the rotation periods of Mercury and Venus

Search for, and study of, pulsars – Arecibo perfect telescope for this.

6 cm wavelength sky survey

BUT – Could not observe the spectral line of atomic hydrogen at 1.420 GHz. Lots of good science but not central to then current community interests so waning support by radio astronomers except for pulsar search and timing.

1972 – 1974Wire mesh surface replaced by 38,000 aluminum panels

~3 mm surface accuracy achieved => max freq of ~ 6 GHz

0.5 MW transmitter installed at 3.8 GHz for solar system studies

First large (1008 channels, 10 MHz bandwidth) digital correlator for spectral line observations .

Some major results:

Discovery of the first binary pulsar, PSR1913+16 in 1974, leading to the (indirect) confirmation of gravitational radiation and the Nobel Prize for Joseph Taylor and Russell Hulse in 1993

First “high resolution” view of the surface of Venus

Mapping of the distribution of galaxies in the nearby universe from HI observations

Discovery of the first millisecond pulsar

Discovery of the first planets about another star – a pulsar

Discovery of the first OH mega masers

First high resolution images of a NEA

Early 1980s – how to overcome limitations due to line feeds?

Line feeds: Intrinsically narrow band so need to build new one for every frequency

Geometric optics determines length but wavelength determines size and spacing of radiating slots plus waveguide diameter

Not possible to build line feeds above ~ 3 GHz due to tolerance issues but reflector surface probable usable up to 10 GHz

Significant reduction in Aeff/Tsys at high zenith angles

Solution: Do spherical aberration correction with mirrors - wavelength independent

Spherical reflector optics

Gregorian Optics

Gregorian Upgrade 1993 –1997

1 – Ground Screen to reduce spillover noise2 – New drive systems including active tie-downs3 – Replace line feeds with a reflector feed system4 – New receivers5 – New S-band transmitter with twice the power6 – Improve surface accuracy of reflector to reach 10 GHz

Gregorian Upgrade 1993 –1997

1 – Ground Screen to reduce spillover noise2 – New drive systems including active tie-downs3 – Replace line feeds with a reflector feed system4 – New receivers5 – New S-band transmitter with twice the power6 – Improve surface accuracy of reflector to reach 10 GHz

RESULT: A modern telescope with greatly improved capabilities

Was the Gregorian upgrade enough?

Needed better instrumentation to utilize the new capabilities.

Result: The Arecibo L-Band Feed Array (ALFA) and new spectrometers

ALFA Receiver MOCK Spectrometers

Major results from the Gregorian Upgrade and ALFA:

The ALFA galactic and extra-galactic surveys

Discovery of binary and triple near-Earth asteroids (NEAs)

Verification of the Yarkovsky and YORP effects via near-Earth asteroid astrometry

Discovery of cm-wavelength molecular lines in ARP 220 and other ULIGS

Discovery of a neutron star (pulsar) with a mass of ~1.7 solar masses allowing constraints on the equations of state of ultra dense matter

Participation in VLBI observations where the processing is done in real time – e-VLBI.

And many more

40 years of innovation has kept the 305 m telescope contributing at the forefront of astronomical research

WHAT NEXT

Keeping Arecibo at the forefront - Current and future projects

Ionospheric interaction facility: Basically plasma research studying non-linear effects in the ionospheric plasma.

Project cost ~$2M

MAJOR INSTRUMENTATION PROJECTS

Six transmitters at 5 and 8 MHz

MAJOR INSTRUMENTATION PROJECTS

12 to 18–m Antenna

Research:

Phase reference antenna for VLBI at X-, C- and L-bands

Potential use for geodetic VLBI at X- and S-bands

Education: Support local education programs

Remotely controlled antenna for student use

12 or 18 m antenna for VLBI phase referencing

12 m Patriot prime focus antenna at site of 64 m Parkes telescope, AustraliaCost ~$600k

Potential site of the antenna at Arecibo

Science Drivers for high sensitivity , high angular resolution VLBI:

Neutron Star Astrometry:- Measuring astrometric parameters: position, proper motion, trigonometric parallax.

- Proper motions yield the identification of birth sites, independent age estimates and velocity determinations (in combination with distances) allowing tests of models for the natal kicks.- Parallaxes provide model-independent distance estimates, testing suggested associations with SNRs, stellar clusters, runaway stars, etc.

Young Supernova Remnants:- Imaging giving angular expansion and deceleration rates for young SNRs Gamma-ray Burst Afterglows:- Measurements of angular expansion and deceleration rates for GRB afterglows allowing evaluation of the surrounding environment. Proper motion measurements can be used to examine the importance of jet emission.

What will follow the ALFA 7-beam 21 cm system?

Beam forming focal plane array at 21 cm – 40 beams on the sky will give very high survey speed

FY2009 start on developing specifications and feasibility/design study – meeting next week in Ithaca

Do work in cooperation with other groups in US and Canada with input from Australian and European groups

MAJOR INSTRUMENTATION PROJECTS

Arecibo L-Band Feed Array

ALFA 7-beam footprint on the sky - field of view is only sampled in certain locations, it is not fully sampled.

To maximize the information that can be obtained by a given telescope about the sky brightness distribution, measurements should be made every half beamwidth. This cannot be done with a cluster of horns like the 7-horn ALFA system.

Calculated beam pattern on sky Measured beam pattern

Rectangular41 Beams

AO40 Sky Footprint Layout

Hexagonal 41 Beams

Survey speed of a telescope – a figure of merit if you want to do a blind survey of a large section of sky looking for e.g. galaxies with detectable amounts of atomic hydrogen – is given by:

Survey Speed: Enter AO40

L-Band Nb Wb BW AeffTSYS

AEFF/TSYS SVS/AOSVS

[deg2] [MHz] [m2] [K] [m2/K]

AO 1 0.0028 300 32750 25 1310 1

ALFA 7 0.0028 300 32750 25 1310 7

AO40 40 0.0028 300 32750 35 936 20.4

# of beams Bandwidth

Beam Solid Angle

19 Dipole system under test at NRAO Green bank by Brigham Young University and NRAO groups.

300 MHz bandwidth systems being developed by the Australian SKA project for the ASKAP array and by the Dutch for installation on the Westerbork Array.

Australian ASKAP checkerboard array

BWTA

FoM fovsys

eff W

2

Survey Speed Figure of Merit

(Ae)2 (Tsys)2 FoV BW FoM

AO1 1 1 1 1 1

ALFA 1 1/1.4 7 3* 14*

AO40 1 1/4 40 3 30

APERTIF 1/41 1/4 1800 3 33

ASKAP 1/170 1/4 8800 3 36

Assumes Tsys of 50K for Phased Array Feeds.

Arecibo’s AO40 Architecture Components

1. Gregorian Optics

2. Array Elements

3. LNA’s

4. Cryogenics

5. Signal Transport

6. Beam Former

7. Spectrometer

A very complex task ! Figure by G. Cortes

Major science drivers for the AO40 Phased Array Feed:

Very high sensitivity survey of the local universe for HI “haloes”

High sensitivity mapping of the Galaxy in HI

Continuum full Stokes polarization mapping of the sky

Deep search for pulsars

MAJOR INSTRUMENTATION PROJECTS

Wide-band 300 MHz to 3 GHz feed development by German Cortes (NAIC, Ithaca)

Potential use on the 305 m telescopePotential use of 1 to 10 GHz version for the 12-18 m VLBI antennaPotential use for the SKA

MAJOR INSTRUMENTATION PROJECTS

Arraying of the WAPP and MOCK spectrometers for use with a single pixel feed to give very high resolution spectra over 1 GHZ or larger bandwidths.

Major application to:

Search for cm wavelength molecular line from external galaxies

Search for cm wavelength molecular lines in our own galaxy

Upgrading of VLBI recording instrumentation

Expanding the IF bandwidth

Education and Public Outreach

~100,000 visitors each year

Strong K-12 educational effort through the Inspiration for Science contract with the Puerto Rican Dept. of Education

Proposal to the Dept of Education for a teacher training program in preparation

Proposals to the NSF in conjunction with the University of Texas at Brownsville for new displays, etc

Expansion of the visitor experience at the Observatory

Expansion plans for the Angel Ramos Visitor Center

Arecibo has a lot going for it:

Most sensitive single dish radio telescope at frequencies up to 8 GHz - five times more sensitive than the GBT

Very modern instrumentation

Very diverse programs and capabilities in:

Radio astronomy Solar system studies Atmospheric science

A proposal over subscription rate of 3 to 4

A great staff

Major problems:

NAIC Facing significant budget reductions over the next two years