Thursday, 25 August 2016

Northern Lights Season has started!


The photo above was captured last night (24th August 2016, at 21:00 UTC (00:00 EEST) by one of the time-lapse cameras we operate jointly with Site-Eye Ltd, UK. The night sky is still too bright at the latitude of Sodankylä to get good contrast, but the season has definitely started. The scientific auroral all-sky camera will return in the near future for real-time monitoring. In the meantime, the time-lapse camera can be used for a look to the north from Sodankylä.

Photo: Site-Eye/SGO, text: Thomas Ulich.

Wednesday, 10 August 2016

Absoluuttigravimetrausta Pittiövaarassa


SGO:n omien mittausten lisäksi observatorion tiloissa toimii myös useiden yhteistyökumppaneiden mittalaitteita. Eräs kotimaisista yhteistyökumppaneista on Maanmittauslaitoksen Paikkatietokeskus (ent. Geodeettinen laitos). SGO:n mittausasemalla sijaitsee GNSS-vastaanottimet, jotka ovat osa kansallista ja kansainvälistä referenssiverkkoa. Laitteet rekisteröivät niin GPS, GLONASS-satelliittit kuin myös uudemmatkin GNSS-järjestelmät, viimeisimpänä kiinalaisten Beidou järjestelmän satelliitteja (suom. Otava).

GNSS-vastaanottimien lisäksi asemalla on absoluuttigravimetripiste, jolla 2-3 vuoden välein tehdään paikalle tuotavalla absoluuttigravimetrillä muutaman päivän havaintosarja, jossa toistuvasti mitataan tyhjiössä pudotettavan prismakappaleen putoamisaikaa, joista huipputarkan kellojärjestelmän, sekä laserilla saatavalla tarkan matkan avulla voidaan laskea absoluuttinen putoamiskiihtyvyys muutaman mikrogalin tarkkuudella. Pitemmällä havaintosarjalla saadaan muun muassa muiden taivaankappaleiden vetovoimien aiheuttamat muutokset painovoimaan mallinnettua pois tuloksista.

Tutkimuspäällikkö Jyri Näränen Maanmittauslaitoksen Paikkatietokeskuksen Geodesian ja Geodynamiikan yksiköstä esitteli absoluuttigravimetrimittausta  SGO:n henkilökunnalle varsinaisen havaintosarjan teon jälkeen. Edessä absoluuttigravimetri, jonka yläosassa prisman pudotuskammi ja alaosassa kulkuajan mittaamiseen käytetty interferometri.


Painovoiman muutos on seurausta maan kohoamisesta jääkauden jälkeen. Sodankylässä maankuori kohoaa noin 5mm vuodessa, jolloin havaintopisteen etäisyys Maan keskipisteestä kasvaa. Samalla kuitenkin tiheämpää ylävaipan materiaalia virtaa tilalle. Muita havaintoihin vaikuttavia tekijöitä on mm. pohjaveden pinnan taso, joka täytyy havainnoissa huomioida. Hitaan muutoksen vuoksi havaintoja tehdään 2-3 vuoden välein, jolloin muutokset on mittaustarkkuuden rajoissa havaittavissa.

Niin, ja se havaittu g Sodankylässä on luokkaa 9.824….. m/s2


Saturday, 30 July 2016

Incoherent Scatter Radar School: Student Presentations and Conclusions

Today was the high point of our incoherent scatter radar (ISR) school, as it was the students' turn to give presentations, while lecturers would listen and ask questions. The 7 groups had half an hour each to present the results of their radar experiments, explaining their scientific motivations and experiment designs, describing the data they had obtained, and discussing on their interpretation.

The talks were really high-level ones; everybody had put a great effort into the task and played the game. Even when the initial scientific targets could not be reached – because of technical problems or too quiet ionospheric conditions – the students managed to come up with a plan B and did a great job in analysing their data sets.

Group 3 studied the polar cap convection with an ESR experiment.
Photo: M. Lavarra

Among the observed phenomena, we had beautiful polar mesospheric summer echoes, electron precipitation, polar cap convection, auroral arcs... And ISR observations were confirmed by measurements from other instruments: ionosonde, SuperDARN, GPS TEC data, satellite observations... 

After closing discussions, it was already time to say goodbye. Most participants are now on their way to Helsinki, spending the night on the train. Hopefully students and lecturers have had a great time in Sodankylä and got to know new potential future collaborators/friends. So, the ISR school is now over... until next time!

Friday, 29 July 2016

Incoherent Scatter Radar School: Analysing Experiment Data

As the end of the radar school is already approaching, a greater and greater part of the programme is dedicated to group work. Yesterday, the morning lectures were essentially focusing on analysing the incoherent scatter radar (ISR) data and fitting the ISR spectrum to extract ionospheric parameters. Other lectures had a more scientific focus and showed examples of ionospheric phenomena which can be studied with ISRs. One more lecture aimed at underlining the importance of keeping a critical view on the analysed data before drawing scientific conclusions.

In the afternoon, the group work on the analysis of Tuesday night's data was continued. Most groups managed to come up with a clear plan on how to divide tasks, which features in the data to focus on, and which additional data sets to look at.

Group 5 looking for particle precipitation signatures in their data.
Photo: C. Heinselman
This all looks very promising for the presentations of Saturday morning. It seems that each group have their own scientific focus, which makes it all the more interesting. Let's see how far they manage to get by this evening!

Thursday, 28 July 2016

Incoherent Scatter Radar School: Excursion in Luosto

After the experiment night, it would have been hard to attend lectures in the morning. So instead, an excursion was organised in Luosto. Students and teachers were divided into six teams and took part to a treasure hunt around the Ahvenlampi pond. With each step came a short text about a "Finnish Fun Fact", along with a related question aimed for providing a few insights on Finnish culture.

Initially, the weather was very nice, and there were only few mosquitoes. Participants came across a lot of bilberries, and several of them could even find cloudberries. The end of the treasure hunt was however somehow precipitated by the arrival of a thunderstorm with heavy rain. Coffee was served in the small laavu where the whole party just fit, before all retreated to the restaurant of the local hotel. As a souvenir, participants were all given a small amethyst stone from the Lampivaara mine – the only active one in Europe – located a few kilometres away from Ahvenlampi.

The Red team fishing a hint.
Photo: C. Heinselman

Lectures resumed in the afternoon, and students could then download the data of their experiments and started to analyse them. In the evening, the workshop banquet allowed our guests to try poronkäristys (sautéed reindeer) and cloudberry pannacotta. Those who were not completely exhausted after the experiment night and the morning treasure hunt were also given the opportunity to experience Finnish sauna at the observatory.

And we are half-way through our radar school already!

Wednesday, 27 July 2016

Incoherent Scatter Radar School: Experiment Night

One of the highlights of the Radar School is the experiment night, which took place yesterday. The participants were divided into groups of 5 to 6 people and had to design a radar experiment to be run using EISCAT.

After the morning lectures providing students with some background on the incoherent scatter theory, pulse coding and experiment configuration, each group was asked to come up with a scientific focus related to the ionosphere (study of a particular region, feature, or process). Based on their topic of interest, they had then to discuss what kind of trade-off they could reach in order to obtain the best possible data. Which altitude and latitude do they want to observe? Is there a preferred magnetic local time for the features they are interested in? What time and range resolution do they need? Is there an optimal pointing direction or scanning pattern in their case?

Once the group agreed on the answers to those questions, they could write a proposal of experiment for either the EISCAT mainland VHF radar or the EISCAT Svalbard Radar (ESR), and request a 2-hour time slot between 17:30 and 01:30 local time. The proposal needed to mention which experiment code should be run, and the desired pointing direction. All those details were submitted to the lecturers, who evaluated them and notified acceptance within 10 minutes, to start with the first experiment less than 30 minutes later (as someone pointed out, this is a once-in-a-lifetime situation!).

Monitoring the polar cap convection with ESR.
Photo: E. Turunen

The experiments were run from the lecture hall of the Polaria building in SGO, by the students themselves, under the supervision of lecturers with experience as EISCAT users. The experiment time slots were intertwined with "radar walks" around Tähtelä, during which the main on-site instruments were briefly presented (and local mosquitoes were properly fed).

During one of the "radar walks" at SGO.
Photo: C. Heinselman

For the rest of the week, participants will retrieve and analyse their data. More on that in the coming days!

Tuesday, 26 July 2016

Incoherent Scatter Radar School: Let's Get Started!

This week, Sodankylä Geophysical Observatory is hosting the Incoherent Scatter Radar School jointly organised and sponsored by EISCAT/SGO and the National Science Foundation (NSF)/SRI International. A total of 39 participants coming from institutes over 13 countries (and of 20 nationalities), are taking part in this radar workshop. The summer school also involves 15 motivated lecturers and organisers from Europe and the United States.

Most participants arrived on Sunday morning, after a night on the train between Helsinki and Rovaniemi (oh yes: to make it easier, we managed to get Rovaniemi airport closed this month). As the bus was heading to Sodankylä, most of them crossed the Arctic Circle for the first time in their lives.

Once in Sodankylä, and after having a delicious lunch and settling down at the student accommodation at Lapin Ammattiopisto, those who were interested were given the opportunity to take part in a walking tour of the village. The weather was exceptional, which certainly contributed to encourage our guests to try salmiakki icecream in front of the K-supermarket. Tervetuloa Suomeen!

The EISCAT receiver in Sodankylä (a little bit hidden behind a group of people)
Photo: T. Ulich

The official programme started yesterday morning with lectures presenting Sodankylä Geophysical Observatory and introducing ionospheric physics and basics of radar theory. In the evening, a small home-made radar demonstration showed how with relatively simple electronics and computing power it is possible to measure the speed or the range of a given target.

This has been a very promising start, and there is even more to come. To be continued...