2012 DA14 Uutiset

Asteroidin harvinaista ohilentoa seurataan SGO:n ja NASA:n yhteistyössä



(English summary below)

Asteroidi 2012 DA14 ohittaa 15. helmikuuta maapallon pinnan erittäin läheltä, 27 700 kilometrin päästä. Sodankylän geofysiikan observatorion tutkijat Juha Vierinen ja Lassi Roininen mittaavat ohilennon aikana Norjan Tromssassa sijaitsevalla EISCAT-järjestön suurtehotutkalla asteroidin ratakehitystä, pyörimistä ja muotoa.

Asteroidin Maan painovoimakentässä muuttunut rata pystytään tutkamittauksilla määrittämään erittäin tarkasti, ja täten uusi rata voidaan ennustaa. Mittaukset on suunniteltu yhteistyössä Tampereen teknillisen yliopiston professori Mikko Kaasalaisen ja EISCAT-järjestön fyysikko Jussi Markkasen kanssa.

Myöhemmässä ohilennon vaiheessa asteroidi tulee Amerikan sektorin tutkien näkyviin. NASAn tutkijat pystyvät käyttämään EISCAT-tutkalla mitattuja arvoja hyväkseen ja jatkavat asteroidin mittaamista suurtehotutkillaan loppuohilennon ajan.

Asteroidin läpimitta on noin 50 metriä. Asteroidin voi havaita maanpinnalta kiikareilla tai kaukoputkella, mutta paljaalla silmällä asteroidia ei erota.


English summary

Of the 15th February, asteroid 2012 DA14 will pass very close (27,700km) to the Earth. Finnish researchers Juha Vierinen and Lassi Roininen from Sodankylä Geophysical Observatory will measure the fly-by from the EISCAT radar facility in Tromsø, Norway. The observations will accurately measure the change in the orbit, as well as rotation and shape parameters.This sophisticated experiment has been designed in cooperation with Professor Mikko Kaasalainen from the Tampere University of Technology and Jussi Markkanen from the Finnish EISCAT station at SGO.


Web link

Press-release (Finnish language)

2012 DA14 radar parameters

EISCAT pointings for the asteroid pass. Based on the energy to noise ratio, we estimate that we can observe until 01:00 UT before losing signal. The vertical lines indicate when the different radars start observing (solid=EISCAT, long dashes=Haystack, short dashes=Goldstone).

Right now I'm doing some programming to allow EISCAT to track the asteroid during the pass. This will involve translating NASA Horizons ephemeris tables into pointing commands that are given to the radar -- possibly involving offsets. With recent observations, the errors are getting smaller and smaller, which increases the chances of hitting the target. Luckily our radar is so small, that the 0.1 degree 3-sigma errors are already much less than the 0.5 degree antenna beam width.

As you can see from the figure above, the asteroid will appear from the East and then head approximately towards zenith. The target will be fast, but not even close to the limits of the tracking speed of the radar. I've estimated the radar cross-section by assuming it is 0.1 times that of a metallic sphere with a diameter of 50 meters. I've estimated the energy to noise ratio based on a 0.1 second coherent integration time and a 12.5% duty-cycle (the maximum that EISCAT can do).

As for coding, I intend to use 200 different codes with a 10 us baud length and the EISCAT maximum 2 ms pulse length. This is to allow a real-time analysis, but still leaving quite many phase transitions for high resolution analysis. I'll be sampling at 10 MHz, which covers the 7 MHz receiver bandwidth at EISCAT. 

Current status at KAIRA

An expedition has gone from the institute up to the EISCAT facility at Tromsø, Norway, to carry out radar observations of this weeks near-miss fly-by of asteroid 2012 DA14. On the way, the team passed the KAIRA site... still happily and reliably observing! Here is the photograph showing the site conditions.

KAIRA site, as of 10-Feb-2013. (Photo: Lassi Roininen)

Like the asteroid and earth, the photo was taken during a "near-miss" drive-by. The vehicle passed within a couple of hundred metres of the site, but there was no risk of collision! ;-)

2012 DA14 Flyby

The asteroid 2012 DA14 will zoom past our planet on the 15th of February at about 20 UT. What makes this even special, is that it passes us really close, about 28000 km from the surface of Earth. Keep in mind that the satellites  that broadcast satellite tv are at about 36000 km. You can see some fun facts about the asteroid on the youtube video prepared by NASA above.

The fact that this asteroid is passing us so close, means that we have a chance of measuring it with the EISCAT UHF incoherent scatter radar. We also happen to be approximately on the same side of Earth as the asteroid will pass, which will allow us to measure it very close to its nearest point. With some luck, next week we will have radar echos of the asteroid show you. 

Gloaming

Just a nice photograph to end the week. We hope you all have a nice weekend!

Arctic twilight. (Photo: D. McKay-Bukowski)

Snowmen

Okay, not from real snow... these little guys were made of white chocolate, desiccated coconut, currents and chips of candied orange.

Some (temporarily) surviving snowmen. (Photo: D. McKay-Bukowski)

Aerial photograph of KAIRA

Our colleagues at EISCAT_3D have posted on their weblog an article about the first high-resolution aerial-photograph of the KAIRA site.

The author (Thomas Ulich) wrote:

" We just learnt that the MapSite of the Finnish National Land Survey (Maanmittauslaitos) has updated aerial photography from the Kilpisjärvi area where the Kilpisjärvi Atmospheric Imaging Receiver Array (KAIRA) is located. The images were taken in late summer 2012, and astonishingly one can just about make out the 3m x 3m ground planes of the LBA aerials in the circular area south of the HBA tiles. "

Also in their article is a link to the high-resolution image of the KAIRA location on the MapSite directly. Note that the images are copyright of the Finnish National Land Survey.