Ooty Radio Telescope

P.K. ManoharanRadio Astronomy Centre
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research
Ooty 643001, India
mano@ncra.tifr.res.in

IPS Workshop
STEL, Nagoya University
23 – 24 November2013

National Centre for Radio Astrophysics
Tata Institute of Fundamental ResearchObserving Facilities
Giant Metrewave Radio Telescope
Ooty Radio Telescope

Radio Astronomy Facilities• Giant Meter wavelength Radio Telescope (near Pune)––––

Multi-frequency synthesis imaging system
25-km baseline
30 antennas of each 45 m diameterIn the NCRA campus, 15m antenna (various Radio Physics Lab. projects)• Ooty Radio Telescope (southern part of India)– Observing frequency 327 MHz– Steerable antenna of size 530m x 30m parabolic cylindrical antenna– Various astronomical observations and solar wind studies– Callisto Solar Spectrograph (part of worldwide radio net)
• Frequency range 45 – 890 MHz• 300 kHz – each channel bandwidth• solar radio spectrograph– Muthorai Radio Telescope – for dedicated solar observations• 290 – 350 MHz• Steerable antenna of size 92m x 9m
• fixed-frequency solar observations (high temporal resolution ~1 ms)

Ooty Radio Telescope (ORT)•Latitude: 11°23’ North Longitude:
76°40’ East•

Equatorially mounted, off-axis
parabolic cylinder•

530m (N-S) x 30m (E-W)•Reflecting surface made of 1100
stainless steel wires•

Feed – 1056 λ/2 dipoles•

E-W Tracking and N-S Steering of
ORT (~9.5 hours, ± 60o)

IPS measurements - advantages• High sensitivity• tracking• good declination coverage• less radio interference in this region

Operated byRadio Astronomy Centre
National Centre for Radio Astrophysics
Tata Institute of Fundamental Research(NCRA-TIFR)

OotyRadio
Telescope(ORT)• 530m (N-S) x 30m (E-W) – east-west tracking of ~9.5 hours• North-South beam steering (± 65 deg. declination)• High sensitivity, S/N ~ 25 (1s integration, BW 4 MHz)

http://rac.ncra.tifr.res.in

Reflector is made of 1100 thin ss wires

Linear array of dipoles 1056
- LNA behind each dipole- 4-bit phase shifter for a dipole
Operating frequency 326.5 MHz- LO 296.5 MHz- IF 30 MHz
22 Modules (N1-N11 and S1-S11)- 48 dipoles in each module

Analog beams – 12-beam system- 3 arcmin separation- covers 2o x 36’ sky- total-power mode
- correlated-beam modeORT Correlated Beam ShapeCurrent Observing Programs with the ORT• Lunar occultation (initial period of ORT)
• Various Pulsar studies• VLBI (ground and space)• Radio recombination line works• Radio transients, etc.
• Interplanetary Scintillation (IPS) Measurements•plu

e-Callisto – Worldwide Radio Network
24-hour Solar Observing
HumainBelgium

Irkutsk,Russia

San JoseCosta Rica

Green Bank
WV, USAKASIS. Korea
Zurich, Bleien
SwitzerlandOoty, IIA, PU
India

MexicoINPE,
Brazilmeasurements: type II radio bursts, CMEs, shock waves, type III bursts etc.

Data available at http://www.e-callisto.org/

Ooty e-Callisto

Upgrades for Ooty Radio Telescope
In collaboration with Raman ResearchInstitute, Bangalore

ORT upgrade –Phase I
ORT as a 44-element programmable telescope– Digitize RF from 44 half modules (11.5mx30m section of ORT)
– 44 numbers of Stage 1 and Stage 2 amplifiers, respectively, atthe feed and at the bottom of the telescope– Transporting signal via fiber optic link

– A distributed signal processing chain (12-ch A/D converts withXilinx Spartan-6 FPGA-based pre-processing capability)– RF digitization tested for all half modules, data transfer overoptical fibre to central computers completed– Software offline FX correlator developed and tested

Phase I

Phase I

Phase I – 44 half-module signals

ORT upgrade –Phase II
Major components– ORT has been configured as a 264-element programmable
telescope• To digitize RF for every 4-phased dipoles (2m x 30m section; 264
sections along the feed of ORT)

– 264 pre-amplifiers and a set of 264 low-loss cables bringRF outputs of pre-amplifiers to the fixed enclosures– 264 Stage-II amplifiers plus filter (to provide ~80 dB gain)– Fiber optic communication for distributing clock and data
between central receiver and base of each modulePhase II

ORT – Recent upgrades – sensitivity and field of view
• 2 Phases• Digitize RF from every 24 phased dipoles (~12-m section)• Digitization of 4-phased dipoles (~2-m section)• Field view 27 deg.
• Full 264-element programmable system• Software-based FX correlator

Parameter Current
Phase-1
Phase-2
Bandwidth 4 MHz
18 MHz 40 MHz
FoV
2.3° x 2.2° 2.3° x 4.6° 2.3° x 27°
Sensitivity
81 mJy40 mJy12 mJymJy(τ = 1 s)

Science with new Programmable Digital Receiver
ORT – a new versatile system for many astrophysical studies
IPS with ORT• wide field of view (2° x 27°) – within the field of view, numberof beams can be formed (or beam can be formed at any given
direction of the scintillating source)• at a given time (~2-3 min of observing time) several
scintillating sources can be observed• provides increased spatial resolution of the sky coverage• Improved tool for space weather Studies (physics ofpropagation of solar eruptions)Interplanetary Scintillation
High sensitivity of ORT allows day-to-day IPS monitoring oflarge number of compact radio sources

Ooty IPS at 327 MHz• Sensitive to solar wind irregularities scale size of ~10 – 500 km• Heliospheric coverage• 10 – 250 Rsun
• at all helio latitudes
For each source- estimation of• power spectrum• scintillation index
Suitable calibration provides• solar wind velocity• density turbulence level

Lines of sight typically observed in a day(2-AU cube)

Distribution of IPS Sources

85% of Sources ≤200 mas~4500 sources

Spectral Power (dB)

Temporal Frequency (Hz)Spectral Power (dB)

Temporal Frequency (Hz)Spectral Power (dB)

Temporal Frequency (Hz)IPS – Power Spectrumρ r, t   ΔI(ro , t o ) ΔI(ro  r, t o  t)
1 PI ρ(0, t) exp( i2π f t)dt
2π 
1  m  2  PI (f)df I  2

Solar wind Density Turbulence
Density Turbulence* Scintillation index, m, is a measure of level of turbulence* Normalized Scintillation index, g = m(R) / <m(R)>* Quasi-stationary and transient/disturbed solar wind
• g > 1  enhancement in Ne• g  1  ambient level of Ne• g < 1  rarefaction in Ne

Scintillation enhancement w.r.t. the ambient
wind identifies the presence of the solar windtransient (CME/CIR) along the line-of-sightto the radio source

IPS temporal power spectrum
IPS – intensity fluctuations are caused by the solar winddensity turbulence - time series transformation provides
the temporal power spectrum

2dzqz222β  αP(f)  (2π r e λ) dq4sinV(q,z,θ)Rqy V (z)  2k pz

Spectral Power (dB)

Temporal Frequency (Hz)Spectral Power (dB)

Temporal Frequency (Hz)Spectral Power (dB)

Temporal Frequency (Hz)Spectral Power (dB)

Temporal Frequency (Hz)

Density Turbulence Spectrum“Interplanetary Scintillations” (IPS)

intensity fluctuations caused by the solar wind densityturbulenceThis time series transformation provides the temporal
power spectrum

 is wavelength of observation; re is classical electron radius.
Fdiff(q) = Fresnel diffraction filter (attenuates low-frequency part of the spectrum)
FSource(q) = Brightness distribution of the source (attenuates high frequency part)Axial Ratio of Irregularity
When the density irregularities are field aligned andapproximated with an ellipsoidal symmetry, thespatial spectrum of density fluctuations, ΦNe(q), for aradio source with the finite size, θ, will be

AR is the ratio of major to minor axes (axial ratio),which is the measure of degree of anisotropy ofirregularities (α power-law index. qi cut-off scale i.e.,
inner-scale size).

Interplanetary scintillation spectra
Fresnel filter knee

Power (dB)

Power law q-(α+1)

Logarithmic temporal Frequency (Hz)
Source size andInner-scale filte

Solar Wind Density Turbulence and Speed (3 days)

2003

Current 3D Ooty Density Reconstruction

The left movie shows an ecliptic cut through the 3D Ooty IPS density reconstruction and theright movie show a meridional cut (from East of the Sun-Earth line) of the same; bothwith the Earth on the right-hand side and it’s orbit shown in each caseThank You