Two Sodankyläläistä in Oulu (cont.)

After four days in the University of Oulu, the premises start to appear less and less hostile and labyrinth-like, and most of our brain capacity can thus be allocated to the modern statistical methods.

They were all gone

The topics covered during the summer school provide a valuable overview of the tools and techniques that any scientist who deals with data may need to implement someday.

The first day was mainly an introduction to the concepts of probability, likelihood and statistics, with a particular focus on the two possible paradigms (frequentist and bayesian) and their different philosophies. The second day, the lectures dealt with parametric modelling and statistical inferences, while the main topic of the third day was regression and curve fitting. Finally, measurement uncertainty analysis, Markov Chain Monte Carlo methods, time series analysis and spatial statistics were on the programme of the last two days.

The Secret Map

Every afternoon, a couple of hours were dedicated to practicals directly related to the examples considered during the lectures. These exercises were implemented in R. R is a free software programming language specially designed for statistics, which contains a great amount of useful packages. In addition, R enables to obtain nice and highly-tailorable plots.

TOO OPTIMISTIC PRIORS

About forty students were taking part to this summer school, with various backgrounds from biology to quantum physics. As not everybody knew one another, a "get-together" evening was organised by Exactus at some bar downtown on Wednesday evening, with a concert of the Groovesisters, a local duo (keyboard and drums). It turned out that, albeit statisticians, the organisers had set slightly too optimistic priors regarding the number of students who would join in. As only eleven of them showed up, and as about eighty free-drink tickets had been bought, let us say that we did not run short of beer...

It was slightly cloudy

After this pretty intense yet fruitful week, the homesickness has become unbearable, and soon will we be driving north to enjoy the colourful ruska and go picking lingonberries.

X-band weather radar installation continues

Yesterday and today, we have assembled transmit/receive system for our experimental X-band weather radar. The system is based on two USRP N210 software -defined radios with Basic Rx and Tx daughterboards. A cylinder Mac titled "Freud" is used for control and data analysis.

We have now proceeded to the point, where we have successfully transmitted and received signals. However, as this a weather radar experiment, we simply see the signal jumping directly from Tx to Rx. Hence, we are waiting for "good" weather, which in this case means rain.

First received signal.

During the installation, we were asked to make proper safety arrangements. I used this possibility to purchase my very first blinking orange light (typically used in professional vehicles and alike). This is to show when the radar is operational and when not. In addition, for amusement, I purchased a "siren" :) !!!

Safety items and the transmit/receive system.

We will report further development as soon as we get a proper target!!

Two Sodankyläläistä in Oulu

This week, the Exactus doctoral programme of the University of Oulu Graduate School (also known as UniOGS) organises a summer school around modern statistical methods for natural scientists. Exactus coordinates the doctoral training of students preparing a PhD in so-called "exact sciences", namely astronomy, physics, chemistry, mathematics and statistics. Incidentally, two of the members of the SGO staff who are currently preparing their PhDs within the Exactus doctoral programme are taking part to this summer school.

Statistics can provide the scientists with highly-valuable tools and methods which may not seem absolutely straightforward at first glance to the neophyte. Yet, the most confusing aspects encountered during the first day turned out not to be mathematical ones but had rather to do with finding directions inside the university buildings.

Entering the R gate

A FOUR-STOREY BUILDING

Let us just recall a few key figures. Slightly more than 15,000 students are studying in the University of Oulu. Population of Tähtelä: about 60 people (during working hours, in the peak season). Characteristic dimensions and main facts of the Polaria main building in Sodankylä: 60 x 60 x 7 m, two storeys, two corridors, about thirty rooms. In comparison, the Linnanmaa campus main building is more of the order of 300 x 400 x 15 m, with four storeys, too many corridors and an infinity (or so) of rooms. No wonder why such a vast and overcrowded place traumatised those two Tähtelä guys far more than the Bayesian inductive learning approach (and its implementation in R) to predict the color of the next ball drawn from a box given the outcome of a first observation.

We were clearly outnumbered

Hopefully, by the end of the week, the probability to reach the next lecture room without getting lost given the location of the previous one will be of the same order as the probability of being eaten by mosquitos while wandering by the Kitinen river in July.

To be continued...

X-band weather radar installation

For information of all the Tähtelä society, residents and visitors:

This week, SGO will install a 10 GHz experimental weather radar. Installation location is next to the meteor radar, i.e. on the left-hand-side of the road, when coming to Tähtelä. A strictly no-access-zone will be marked clearly. Access is strictly forbidden due to microwave radiation hazard! Notice especially: During experiments, you are not allowed to be near by the back-side of the transmitter! The purpose of the radar installation is the development of radar transmission coding and analysis methods. The installation is temporary. The objective is to install the radar to the upper structures of the 32-metre EISCAT antenna. 

X-band experimental weather radar in Tähtelä, Sodankylä.

Revontulikausi alkanut

Kaikki SGO:n revontulikamerat mukaanlukien Abiskossa oleva EMCCD-kamera, on nyt toiminnassa ja kuvaavat taivasta auringon laskusta nousuun. Ensimmäisen havaintoviikon aikana revontulet oli tunnistettavissa Sodankylän kameran kuvista yhtä yötä lukuunottamatta, tosin parina yönä reposet oli pilviverhon takana. Kamera kuvaa taivasta kolmella eri suotimella sekä ilman suodinta. Näyttävin show oli sunnuntain ja maanantain välisenä aamuyönä, jonka kuvista koostettu elokuva on alla.

Tällä hetkellä Sodankylässä kamerat aloittaa kuvaamisen puoli yhdentoista jälkeen illalla, jolloin kuvat alkavat myös päivittyä SGO:n www-sivuille ja mm. AurorasNow!-sivustolle. Kyseisillä sivuilla päivittyy revontulen vihreän valon aallonpituuden (557.7nm) suotimella otettu mustavalkoinen kuva. Loppuviikosta kuvassa alkaa näkymään myös kasvava kuu, joka vaikeuttaa heikkojen revontulien havainnointia paljaalla silmällä.

Briefly in English:

All SGO imagers are now in operation after EMCCD imager at Abisko station was started in the end of the last week. Auroras can be picked from six of the seven nights, when the iCCD camera has been in operation. Quite nice start for the aurora season! Couple of nights were cloudy, but still the green emission of the Northern Lights illuminated trough the clouds to the imager. So far the best show of the season was the night of Sunday-Monday. Check the video!

Perfect Pulse-compression for Continuous Waveforms

We report that our paper on perfect pulse-compression technique has been published in Inverse Problems and Imaging. The reference is:

L. Roininen, M. Lehtinen, P. Piiroinen and I. I. Virtanen, Perfect Radar Pulse Compression via Unimodular Fourier Multipliers, Inverse Problems and Imaging, 8 831-844 (2014).

This study is continuation of the perfect coding technique papers reported originally in the same journal:

M. Lehtinen, B. Damtie, P. Piiroinen and M. Orispää,  Perfect and almost perfect pulse compression codes for range spread radar targets, Inverse Problems and Imaging, 3 465-486 (2009).

L. Roininen and M. S. Lehtinen, Perfect pulse-compression via ARMA algorithms and unimodular transfer functions, Inverse Problems and Imaging, 7 649-661 (2013). 

The major new contribution in Roininen et al. 2014 paper is in extending the perfect coding technique to continuous waveforms.

ABSTRACT:

Perfect Radar Pulse Compression via Unimodular Fourier Multipliers

We propose a novel framework for studying radar pulse compression with continuous waveforms. Our methodology is based on the recent developments of the mathematical theory of comparison of measurements. First we show that a radar measurement of a time-independent but spatially distributed radar target is rigorously more informative than another one if the modulus of the Fourier transform of the radar code is greater than or equal to the modulus of the Fourier transform of the second radar code. We then motivate the study by spreading a Gaussian pulse into a longer pulse with smaller peak power and re-compressing the spread pulse into its original form. We first motivate the study with spreading and re-compression  of a Gaussian radar pulse. We then review the basic concepts of the theory and pose the conditions for statistically equivalent radar experiments. We show that such experiments can be constructed by spreading the radar pulses via multiplication of their Fourier transforms by unimodular functions. Finally, we  show by analytical and numerical methods some examples of the spreading and re-compression of  certain simple pulses.

Pictures from Hailuoto

We are going to shamelessly ape the KAIRA blog and post not-so-scientific stuff once in a while especially on weekends. So for this Sunday we present some pictures from Hailuoto (map), an island near to Oulu, where I spent few days couple a weeks ago with Professor Markku Lehtinen in order to finalise our EISCAT3D reports.

It is an excellent place to retreat and to work without distractions.

Marjaniemi lighthouse and the former pilot station which is now a hotel and a restaurant.

Fisher boat on dry land

Sunset in Marjaniemi

Fishermen's huts. We rented two of those. No running water or bathrooms, but enough electricity for our computers.

All pictures by M.O.