1. The Future of the Past Harvard University Astronomy 218 Concluding Lecture, May 4, 2000

2. OVRO, BIMA, PdB 30-m,14-m, 12-m "Radio" Observations of the Redshifted Universe: c. 2000 1 23456789 10 2 10  m 100  m (dust) 3 mm (CO 1-0) 1cm (H 2 O masers) 21cm (HI) 1 m (pulsars, SNR) VLA, Arecibo Redshift Wavelength [cm] JCMT, CSO, HHT

3. "Radio" Observations of the Redshifted Universe: Recent Additions by ~2009 1 23456789 10 2 10  m 100  m (dust) 3 mm (CO 1-0) 1cm (H 2 O masers) 21cm (HI) 1 m (pulsars, SNR) SMA VLA+, GBT LOFAR Redshift Wavelength [cm] LMT GBT

4. "Radio" Observations of the Redshifted Universe: c. 2015 1 23456789 10 2 10  m 100  m (dust) 3 mm (CO 1-0) 1cm (H 2 O masers) 21cm (HI) 1 m (pulsars, SNR) ALMA SKA LOFAR Redshift Wavelength [cm]

5. The Atacama Large Millimeter Array (ALMA) No less than 64 12-meter antennas located at an elevation of 16,400 feet in Llano de Chajnantor, Chile Imaging instrument in all atmospheric windows between 1 cm and 350 microns Array configurations from approximately 150 meters to 10 km Spatial resolution of 10 milliarcseconds, 10 times better than the VLA and the Hubble Space Telescope Able to image sources arcminutes to degrees across at one arcsecond resolution Velocity resolution under 0.05 km/s Faster and more flexible imaging instrument than the VLA Largest and most sensitive instrument in the world at millimeter and submillimeter wavelengths Point source detection sensitivity 20 times better than the VLA

6. Sample SKA Design Specifications A eff /Tsys: 2 x 10 4 m 2 K -1 (or 0.003  a -1 Jy K -1 ) Total Frequency Range: 0.15 - 20 GHz Imaging Field Of View: 1º @ 1.4 GHz Instantaneous Pencil Beams: 100 Separation of Beams: 100º (low ); 1º (middling ) Number of Spatial Pixels: 10 8 Angular Resolution: 0.1” @ 1.4 GHz Continuum Surface Brightness Sensitivity: –1 K @ 0.1” (continuum) Instantaneous Bandwidth : 0.5 + /5 GHz Number of Spectral Channels: 10 4 Number of IF bands: 2 Clean Beam Dynamic Range: 10 6 @ 1.4 GHz Polarization Purity: -40 dB Instr.A eff /T sys 70m145 GBT285 VLA280 Arec1,414 ALMA 98 1HT193 DSNarr 3,547 SKA20,000

7. SKA Scheme for Distribution of Antennas Processor

8. SKA H I Redshift Surveys Number of detected galaxies and volume sampled for a number of recent large galaxy redshift survey projects. Optical surveys are shown in blue and HI(HIPASS) surveys in red. The SKA would sample to greater depths than presently possible, and would sample galaxies in atomic hydrogen, thereby viewing galaxian masses independent of stellar content or star formation history

9. Techniques for the Future On-the-fly mapping Multi-beam arrays Snapshot aperture synthesis (no reliance on Earth rotation) Massive mosaicing Improved "corrections" for short-spacing hole Remote observing Orbiting elements in VLBI