Wednesday, June 19, 2013

Where is SDO?

SDO is in a 28 degree inclined geosynchronous orbit, 36,000 km above Earth's surface. Unlike a satellite in geostationary orbit, which appears to just hover above Earth, SDO actually traces a figure-8 in the sky every day to have a direct line of sight to White Sands, New Mexico, where the two dedicated ground stations are located.

You can always check in and see where SDO currently is here:

How long did it take to plan and design SDO?

It took a little over 10 years to plan and design SDO. More information the multi-phase process below.
Pre-Phase A- 1997 - After the launch of the Solar & Heliospheric Observatory (SOHO) in 1995, solar scientists began thinking about what data they were still lacking that was necessary to do the science that they wanted to do. From this needs assessment and based on lessons-learned from the SOHO build, launch and data they began to develop the preliminary ideas for the next Heliophysics strategic mission. For the SDO, Lockheed Martin, Solar and Astrophysics Laboratory was selected to build and operate the Atmospheric Imaging Assembly (AIA), and to build the Helioseismic and Magnetic Imager (HMI). HMI would be operated and the huge data stream (~4 TB per day) managed at Stanford University, while the University of Colorado, Boulder would build and operate the Extreme Ultraviolet Variability Experiment (EVE).

Phase A- 2002- The deliverable at the end of Phase A is System Concept Study report which contains, more specific instrument requirements, a more complete budget. 

Phase B- 2003- During Phase B, the preliminary plan is converted into a baseline technical solution - requirements are further defined, schedules are determined, and specifications are prepared to initiate system design and development. The deliverable at the end of the phase is the Preliminary Design review document, which sets out very specific requirements for the build and testing of the instruments down to how many threads a bolt will have, and the exact pressure that will be used to attach said bolt.

Phase C and D- Build, Integration and Testing- 2004
Phase C represents the beginning of the implementation stage. The Phase C deliverable is the Critical Design Review
 There is a lot of activity in Phase C including:
·      Procurement of all aspects of the space craft
o   Announcements of opportunity go out in 2005 for technical aspects of the space craft.  These announcements unlike the instrument announcements contain of the design and technical specifications required.
o   Manpower profile peak- All manners of engineers are modeling, building and testing every aspect of the spacecraft for various factors, operations, ability to withstand space, integration with other spacecraft instruments and bus.
o   HMI, EVE and AIA are built onsite at the subcontract locations
·      The Testing of all of the parts of the spacecraft in the thermal vacuum chambers and on the vibration tables to ensure that they are space ready.
Phase D Deliverable is the pre-ship review, and the completed and launched spacecraft.
·      At this point there is a comprehensive audit in which all of the procurements are matched up with budget items and check lists
Launch an initial commissioning takes place during phase D.

Phase E- Science mission and Operations- 2010
During Phase E science data is collected and made available to the public for scientific investigations that take place around the world. The mission is monitored 24 hours a day 7 days a week by the mission operations team at Goddard Space Flight Center. The instruments are monitored and operated at their respective institutions. To date SDO has met minimum mission success, meaning it has fulfilled all of the mission goals. It has taken over 100 million images of the sun and served 4500 terabytes of data.

What is space weather and what research is SDO doing with space weather?

Space weather is (1) the study of eruptive solar activity (solar storms) such as solar flares, coronal mass ejections, solar energetic particles, (2) the effect these storms have on Earth, the rest of the solar system (for example the other planets) and (3) the effect on our technology in space and on Earth.

SDO has provided incredibly detailed observations of the sun and the areas that produce space weather activity. This includes observing the growth of sunspot regions (main flare and major CME producers) as well as the birth of CMEs and the evolution of solar prominences, which often produce large CMEs.  Link to larger version of the picture

How long will it take SDO to complete its mission?

Although it is difficult to determine exactly when the SDO mission will end, we know it will be around for at least another decade.  Once the mission has ended, we will use SDO’s thrusters to move it several hundred miles higher in altitude into a collision-free zone; this is important because we don’t want it to collide with any active satellites and cause them damage.  Once SDO is moved out of its orbit we will turn it off...but luckily that is not going to happen for several more years!  (Fun fact: SDO has enough fuel to keep it in orbit for several hundred years!)
Where is SDO now? Check out its current operations information .

What has been the most surprising discovery SDO has made thus far?

That is a tough one. Here is one surprising discovery for each of the instruments.

AIA: AIA observed a comet travel through the sun’s corona, travel behind the sun and emerge around the other side intact.

HMI: HMI has the first clear detection of emerging sunspots below the solar surface (visible layer called the photosphere) before there is any indication on the surface.

EVE: EVE scientists discovered extra energy in solar flares up to 5 hours after the peak of a flare.

What are the 3 instruments on SDO?

HMI (Helioseismic and Magnetic Imager)

The Helioseismic and Magnetic Imager extends the capabilities of the SOHO/MDI instrument with continual full-disk coverage at higher spatial resolution and new vector magnetogram capabilities.

PI: Phil Scherrer, PI Institution: Stanford University.

HMI will use the acoustic waves and magnetic field measured at the surface of the Sun to study the motions of material inside the sun and the origins of the solar magnetic field.

We use the wave data to study the inside of the Sun. As the waves travel through the Sun they are influenced by conditions inside the Sun. The speed of sound increases where solar material is hotter, so the speed and angle at which the wave is generated determine how far it will penetrate into the solar interior. The shallower the angle, the shallower the penetration; the steeper the angle, the deeper the wave will travel. It takes about 2 hours for a sound wave to propagate through the Sun’s interior. The frequency and spatial pattern the waves make on the surface indicate where the waves have traveled. Scientists learn about the temperature, chemical makeup, pressure, density, and motions of material throughout the Sun by analyzing the detailed properties of these waves.

HMI will provide the first rapid-cadence measurements of the strength and direction of the solar magnetic field over the visible disk of the Sun. Scientists use this information to understand how the magnetic field is produced and, when combined with measurements from AIA, how that field produces flares and coronal mass ejections (CMEs), the storms of space weather.

AIA (Atmospheric Imaging Assembly)

The Atmospheric Imaging Assembly images the solar atmosphere in multiple wavelengths to link changes in the surface to interior changes. Data includes images of the Sun in 10 wavelengths every 10 seconds.

PI: Alan Title, PI Institution: Lockheed Martin Solar Astrophysics Laboratory.

AIA is an array of four telescopes that will observe the surface and atmosphere of our star with big- screen clarity and unprecedented time resolution. It’s like an IMAX® camera for the Sun.
AIA will produce a high-definition image of the Sun in eight selected wavelengths out of the 10 available every 10 seconds. The 10 wavelength bands include nine ultraviolet and extreme ultraviolet bands and one visible-light band to reveal key aspects of solar activity. To accomplish this, AIA uses four telescopes, each of which can see details on the Sun as small as 725 km (450 mi) across— equivalent to looking at a human hair held 10 m (33 ft) away.

Because such fast cadences (number of images per minute) with multiple telescopes have never been attempted before by an orbiting solar observatory, the potential for discovery is significant. In particular, researchers hope to learn how storms get started near the Sun’s surface and how they propagate upward through the Sun’s atmosphere toward Earth and elsewhere in the solar system. Scientists will also use AIA data to help them understand how the Sun’s changing magnetic fields release the energy that heats the corona and creates solar flares.

EVE (Extreme Ultraviolet Variablity Experiment)

The Extreme Ultraviolet Variablity Experiment measures the solar extreme-ultraviolet (EUV) irradiance with unprecedented spectral resolution, temporal cadence, and precision. EVE measures the solar extreme ultraviolet (EUV) spectral irradiance to understand variations on the timescales which influence Earth's climate and near-Earth space.

PI: Tom Woods, PI Institution: University of Colorado.

Solar scientists will use the Extreme Ultraviolet Variability Experiment (EVE) to measure the sun’s brightness in the most variable and unpredictable part of the solar spectrum. The extreme ultraviolet, or EUV, ranges in wavelength from 0.1 to 105 nm.

EUV photons are much more energetic and dangerous than the ordinary ultraviolet rays that cause burns. If enough EUV rays were able to reach the ground, a day at the beach could be fatal. Fortunately, Earth’s upper atmosphere intercepts the Sun’s EUV emissions.

In fact, solar EUV photons are the dominant source of heating for Earth’s upper atmosphere. When the sun is active, EUV emissions can rise and fall by factors of hundreds to thousands in just a matter of seconds. These surges heat the upper atmosphere, puffing it up and increasing the drag on man-made spacecraft.

Wednesday, June 12, 2013

The Sun and Moon

This image is a view of the sun captured by NASA's Solar Dynamics Observatory on Oct. 7, 2010, while partially obscured by our moon. A close look at the sharp edge of the moon against the sun shows the outline of lunar mountains. A model of the moon from NASA's Lunar Reconnaissance Orbiter has been inserted into the picture, showing how perfectly the moon's topology fits into the shadow observed by SDO. Credit: SVS/NASA Goddard You can find more versions of this juxtaposition at the Goddard Scientific Visualization Studio and more information about the image at NASA.

Friday, June 7, 2013

Comet Lovejoy, from SDO to Science and the BBC

The perihelion passage of Comet Lovejoy is described in an article at the BBC. The research article, by Cooper Downs and Karel Schrijver and others, shows how the comet's tail reacts to the coronal magnetic field as it moves along that field. That article appears in Science magazine. Sun-grazing comets that can be seen in the EUV give us a new window on the world of the corona. It is a shame they are rare, but Comet ISON may be a good show this Thanksgiving Day.

Dr. Downs was interviewed on today's episode of Science Friday. It sounded good and a video of Comet Lovejoy is also posted on the site.