1. 1 Brief history of fixed-reflector radio telescopes Richard Strom ASTRON, Dwingeloo University of Amsterdam NAOC, Beijing

2. 2 You will all be familiar with Arecibo; what about its predecessors?

3. 3 And I exclude telescopes like… and… Nançay …Vermillion River

4. 4 1947: Jodrell Bank 218’ (66 m) fixed antenna Built to detect cosmic rays with radar After several years was being used for radio astronomical observations Parabolic shape formed by parallel wires Beam could be shifted by displacing focus

5. 5 1951: Kootwijk ‘kuil’ (pit) antenna 30 m diameter in natural sand pit Built for monitoring transparency of ionosphere Tilted 10  south (Cyg A passed through beam daily) Used for a few test observations

6. 6 1951: Dover Heights “hole-in-ground” Sydney, Australia 22 m diameter Motivation: galactic center passes near zenith Hand excavated (Bolton, Slee, Stanley) in secret (kept from Pawsey) Mapped GC region

7. 7 1957: Katsiveli, Crimea 31 m diameter Concrete base, thin metal coating Accurate surface (10 GHz observing) Reflector tilted to south (to observe Crab and [summer] sun)

8. 8 1965: Arecibo, Puerto Rico 305 m (1000’) diameter Built for ionospheric, radio astronomical and planetary radar studies In karst depression Has been regularly upgraded Major contributions to radio science Largest radio telescope

9. 9 1966: RRE Malvern, UK Designed for ionospheric research 43 m diameter (140’) 400 MHz receiver Never used for radio astronomy

10. 10 1970: Five College Radio Astronomy Observatory In Massachusetts, USA 38 m (120’) diameter, spherical reflector (Arecibo- like) Plan to build 32 such, only 4 were realized Designed for pulsar observing (50-500 MHz receivers)

11. 11 1975-85: ROT54 on Mt. Aragats Radio (54 m) Optical (2.6 m) Telescope In Armenia Used at λ3 cm Innovative (but useful?) Not many published results

12. 12 What were their achievements Jodrell: HB survey; galactic sources are extended; M31 continuum emission Kootwijk: tests (EMI problems) Dover Heights: galactic center region Crimea: λ3 cm map of sun; polarization detected from Crab, sun Arecibo: Many (pulsars, HI, etc.; planetary radar; ionosphere studies)

13. 13 Shortcomings of Jodrell 218’ reflector (and solutions) Single fixed direction Displace prime focus (Jodrell, Dover Hts) Tilt parabolic axis (Kootwijk, Crimea) One linear polarization Mesh/solid reflector (DH, Kootwijk, Crimea) Support of primary surface Depression in ground (DH, Kootwijk, Crimea) Spherical reflector, karst depression (Arecibo)

14. 14 Arecibo, at 50 years, certainly has staying power Lessons from history A large collecting area really helps Ability to observe much of sky is important FAST innovation is its dynamically adjustable parabolic reflector All successful telescopes have undergone regular upgrades Keep things as flexible as possible (within limits) to react to future (technological) developments

15. 15 Thank you! 谢谢