1. Mid Frequency Aperture Arrays
Wim van Cappellen
ASTRON is part of the Netherlands Organisation for Scientific Research (NWO)

2. About ASTRON LOFAR WSRT
Mission: to make discoveries in radio astronomy happen, via the development of novel and innovative technologies, the operation of world-class radio astronomy facilities, and the pursuit of fundamental astronomical research.
LOFAR
WSRT

3. R&D department
Over 60 highly trained professionals working in 6 Competence Groups
Digital & Embedded Signal Processing Group
Computing Group
Mechanical Group
Radio Group
System Design & Engineering Group
Technical Support Group
14 Exabytes/day raw data

4. Technology Antennas RFI mitigation Low Noise Amplifiers Photonics
Mechanics
Photonics
Filtering
Beam forming
A/D Conversion
Digital Signal Processing
Correlation
Calibration
High Performance Computing
Pipelines
Storage

5. ASTRON Past collaborations
SHAO - Bert Woestenburg: cryogenic LNA’s, 6 cm and 21 cm (Li Bin)
Jin Chengjin, Gan Hengqian, Simulation of FAST reflector
Discussions on Phased Array Feed for FAST
Current:
KLAASA in MFAA consortium

7. MFAA
Most important discoveries in astronomy result from technical innovation
[Harwit, 1981]

8. SKA 2 is about exponential growth
Target:
Sensitivity > 10,000 m2/K
Survey Speed > 1.4e10 deg2m4/K2
Innovation is needed for exponential growth

9. Very speculative, but illustrative
Suppose you have 1 B€ to spend. That would probably buy you:
Sensitivity [m2/K]
Survey speed
[deg2m4/K2]
500 dish SPF telescope
3,000 (30%)
13e6 (0.09%)
300 dish PAF telescope
1,000 (11%)
34e6 (0.24%)
MFAA telescope
10,000 (100%)
1.4e10 (100%)

10. MFAA has
A very large field of view, and the opportunity of transient buffering
A fast response time and pointing
Multiple beams, concurrent observations
A very high survey speed capability
High sensitivity < 1.45 GHz
No moving parts
No vacuum, helium, cryogenics
Relatively low post-processing costs
(large stations)

11. Can only be done with an SKA-AAMID telescope
MFAA Rationale
Billion galaxy survey, i.e. high sensitivity and survey speed from 1450 MHz down to z ~3
Very wide field-of-view transient observations, incl. buffering
Timing of very many pulsars (10,000+)
Can only be done with an SKA-AAMID telescope

12. MFAA Key challenges Reducing power consumption Integration
System optimization
Sustainable energy
Calibration down to thermal noise needs accurate beam and sky models to calibrate sources in near and far sidelobes
Algorithm development
Learn from other AA instruments (LOFAR, MWA, SKA1-Low)

13. Antennas - Dense Vivaldi elements Planar - ORA Regular layout
ASTRON
Manchester U.
125mm
pitch
Vivaldi elements
3-layers
Square layout
KLAASA
Planar - ORA
Regular layout
Spacing ~max. frequency

14. 20 K
Technology development is expected to meet the cost and power goals
Demonstrated MFAA up to about 100 m2 level
The next logical and essential step is a science demonstrator

15. Joint research opportunities
Establish a long-term collaboration on MFAA technology research and science, with the goal of realizing an MFAA instrument.
Numerous technology research topics, such as calibration, beam models, LNA design, power efficient computing
Several of these aspects are essential for Phased Array Feeds as well.
On the longer term: MFAA station
complementing FAST
Leverage investments of FAST
Perform unique science
Provides a technology path
towards SKA2
Industry involvement

16. Concluding remarks
Mid Frequency Aperture Arrays is an enabling technology for (survey) radio astronomy around 1 GHz
Steady progress in front-end development, various concepts. Costs and power have been reduced 2-4x over the last 5 years
Reduction of costs and power consumption is key!
MFAA is moving towards a science demonstrator
White Paper: arXiv: