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Measuring atmospheric water vapour level and KEK, Tsukuba, Japan CMB using KUMODeS II 26 May 2017 Gurbir Singh Viraj Karambelkar Yashvi Sharma Indian Institute of Technology, Bombay 1 Introduction KUMODeS II Theory Model LMFit 2

SLIDE 1

Gurbir Singh Viraj Karambelkar Yashvi Sharma

Indian Institute of Technology, Bombay

Measuring atmospheric water vapour level and CMB using KUMODeS II

KEK, Tsukuba, Japan 26 May 2017

SLIDE 2

1 Introduction

KUMODeS II Theory Model LMFit

2 Observations 3 CMB

SLIDE 3

Introduction

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Schematic Diagram of KUMODeS II

SLIDE 4

Introduction

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KUMODeS II

Using KUMODeS II, we measured

◮ Precipitable Water Vapour (PWV)

SLIDE 5

Introduction

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KUMODeS II

Using KUMODeS II, we measured

◮ Precipitable Water Vapour (PWV) ◮ Cosmic Microwave Background (CMB)

SLIDE 6

Introduction

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Theory

◮ Nyquist Theorem

P = kGBT

SLIDE 7

Introduction

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Theory

◮ Nyquist Theorem

P = kGBT

◮ Y factor method

Phot = kGB (Tnoise + 300) Pcold = kGB (Tnoise + 77)

SLIDE 8

Introduction

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Theory

◮ Nyquist Theorem

P = kGBT

◮ Y factor method

Phot = kGB (Tnoise + 300) Pcold = kGB (Tnoise + 77)

◮ Sky Observation

Psky = kGB

Tnoise + Tsky

SLIDE 9

Introduction

images/IM_logo.pdf

Model

Used AM to model the atmospheric emission

SLIDE 10

Introduction

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LMFit

AM + mx + c

Oxygen+CMB

SLIDE 11

Introduction

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LMFit

AM + mx + c

Oxygen+CMB ◮ The parameters were PWV, m, and c.

SLIDE 12

Introduction

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LMFit

AM + mx + c

Oxygen+CMB ◮ The parameters were PWV, m, and c. ◮ The data was fit according to this model using LMFit

SLIDE 13

Observations

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First run

The noise temperature observed was

SLIDE 14

Observations

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Improvement

By replacing a cable, we were able to improve the noise temperature.

Figure:

SLIDE 15

Observations

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Improvement

By installing an isolator, the noise temperature was further improved.

Figure: Block diagram with isolator

SLIDE 16

Observations

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Improvement

Figure: Comparison of noise with and without isolator

SLIDE 17

Observations

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Sky Observations

SLIDE 18

Observations

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PWV fit

SLIDE 19

CMB Measurement

SLIDE 20

CMB

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CMB Measurement using KUMODeS II setup

When the sky is observed using the radio receiver,

◮

Pout = kGB(Tnoise + Tatm × 1 cos(z) + Tcmb) z : zenith angle

SLIDE 21

CMB

images/IM_logo.pdf

CMB Measurement using KUMODeS II setup

When the sky is observed using the radio receiver,

◮

Pout = kGB(Tnoise + Tatm × 1 cos(z) + Tcmb) z : zenith angle Also, from the Y-Factor method,

SLIDE 22

CMB

images/IM_logo.pdf

CMB Measurement using KUMODeS II setup

When the sky is observed using the radio receiver,

◮

Pout = kGB(Tnoise + Tatm × 1 cos(z) + Tcmb) z : zenith angle Also, from the Y-Factor method,

◮

Phot = kGB(Tnoise + 300)

SLIDE 23

CMB

images/IM_logo.pdf

CMB Measurement using KUMODeS II setup

When the sky is observed using the radio receiver,

◮

Pout = kGB(Tnoise + Tatm × 1 cos(z) + Tcmb) z : zenith angle Also, from the Y-Factor method,

◮

Phot = kGB(Tnoise + 300)

◮

Pout − Phot = kGB(Tatm × 1 cos(z) + Tcmb − 300)

SLIDE 24

CMB

images/IM_logo.pdf

CMB Measurement using KUMODeS II setup

When the sky is observed using the radio receiver,

◮

Pout = kGB(Tnoise + Tatm × 1 cos(z) + Tcmb) z : zenith angle Also, from the Y-Factor method,

◮

Phot = kGB(Tnoise + 300)

◮

Pout − Phot = kGB(Tatm × 1 cos(z) + Tcmb − 300) A plot of (Pout-Phot)/kGB vs sec(z) is a straight line with intercept (Tcmb − 300)

SLIDE 25

CMB

images/IM_logo.pdf

Observations

Figure: CMB

SLIDE 26

CMB

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Results

We obtained the cmb temperature spectrum as

Figure: CMB temperature vs frequency

SLIDE 27

CMB

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Conclusions

The cmb result is off from the expected value of 2.7K This is probably because of the following reasons-

◮ Reflections from the mirror and ground

When we plot Tsky vs Frequency, we observe a trend that the sky temperatures increase with time. Also, a standing wave pattern (wavelength 1m approx) is seen in the sky temperatures taken at later times. However, no such increase in temperatures are seen in readings taken inside the building during noise calculations.

SLIDE 28

CMB

images/IM_logo.pdf

Conclusions

The cmb result is off from the expected value of 2.7K This is probably because of the following reasons-

◮ Reflections from the mirror and ground

When we plot Tsky vs Frequency, we observe a trend that the sky temperatures increase with time. Also, a standing wave pattern (wavelength 1m approx) is seen in the sky temperatures taken at later times. However, no such increase in temperatures are seen in readings taken inside the building during noise calculations. Hence, the increase is probably due to reflections from the mirror used to focus the radiation and ground.

SLIDE 29

CMB

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Conclusions

Figure: Sky Temperatures

SLIDE 30

CMB

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Conclusions

SLIDE 31

CMB

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Conclusion

Uncertainty in gain of Amplifier

◮ We have calibrated the gain of the receiver by taking two

Y-Factor measurements, before and after the sky

measurements. Then, we used linear extrapolation to find the

gain of the amplifier during measurement time.

SLIDE 32

CMB

images/IM_logo.pdf

Conclusion

Uncertainty in gain of Amplifier

◮ We have calibrated the gain of the receiver by taking two

Y-Factor measurements, before and after the sky

measurements. Then, we used linear extrapolation to find the

gain of the amplifier during measurement time.

◮ However the gain of the amplifier is extremely sensitive to

temperature, and the gain profile may not be linear. In other telescopes, and even KUMODeS, real time gain calibration is done using a cold body inside the telescope.

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