Swift

Swift Frequently Asked Questions

Questions about the Swift mission and satellite

Questions about Swift science

Questions about the Swift mission and satellite

What is Swift?
Swift is a first-of-its-kind multi-wavelength observatory dedicated to the study of gamma-ray burst (GRB) science. Its three instruments work together to observe GRBs and afterglows in the gamma-ray, X-ray, optical, and ultraviolet wavebands. Swift, part of NASAªs medium explorer (MIDEX) program, was developed by an international collaboration. It was launched into a low-Earth orbit on a Delta 7320 rocket on November 20th, 2004. In 8 months Swift has already observed 45 GRBs, and during its nominal 2-year mission is expected to observe more than 200 bursts, which will represent the most comprehensive study of GRB afterglows to date.
What are the Swift mission goals?
Swift was designed with a number of science goals:
  • Determine the origin of gamma-ray bursts.
  • Classify gamma-ray bursts and search for new types.
  • Determine how the blastwave evolves and interacts with the surroundings.
  • Use gamma-ray bursts to study the early universe.
  • Perform a sensitive survey of the sky in the hard X-ray band.

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How does Swift work?
Swift has a complement of three co-aligned instruments for studying gamma-ray bursts and their afterglow: the Burst Alert Telescope (BAT), the Xray Telescope (XRT), and the Ultraviolet/Optical Telescope (UVOT). The largest instrument on-board Swift is the BAT, which can view approximately a sixth of the entire sky at one time. It will detect approximately 100 or more gamma-ray bursts per year. Within seconds of detecting a burst, the spacecraft will "swiftly" and autonomously repoint itself to aim the XRT and UVOT at the burst to enable high-precision X-ray and optical positions and spectra to be determined. The positions will then be relayed to the ground for use by a network of observers at other telescopes. Swift will determine redshifts for most of the bursts that it detects (allowing scientists to know how far away they are and how absolutely bright they are), and will also provide detailed multi-wavelength light curves for the duration of the afterglow (allowing scientists to probe the physical environment in which the event took place). Key data taken by Swift will be relayed to the ground in near real-time, allowing the GRB Coordinate Network (GCN) to immediately distribute it to the world via the internet for follow-up observations and study. Swift will also use the BAT to perform an all-sky survey of low-energy gamma-rays that will be significantly more sensitive than any previous survey.

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How did Swift get its name?
Swift, unlike most NASA satellites, it not an acronym. Instead Swift is named for a bird of the same name. This bird is special because it can change angles very quickly in mid-flight, like Swift will do. For more information on how Swift got its name check out this answer to Goddard's Science Question of the Day about it.

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How do we communicate with Swift?
The Mission Operations Center (MOC) at Penn State University provides real-time command and control of the spacecraft and monitors the observatory, while also taking care of science and mission planning, Targets of Opportunity (ToO) handling, and data capture and accounting. The Italian Space Agency's ground station at Malindi, Kenya provides the primary communications. Swift burst alerts and burst characteristics are relayed almost instantaneously through the NASA TDRSS space data link to the GCN for rapid distribution to the community.

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Who makes public the data that Swift acquires?
Swift data will be made available to the world via three different data centers located in the United States (the High Energy Astrophysics Science Archive Research Center, HEASARC), the UK (the UK Swift Science Data Center, UKSSDC), and Italy (the Italian Swift Archive Center, ISAC).

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What is the Swift Science Center?
The Swift Science Center (SSC) assists the science community in fully utilizing the Swift data. It is also responsible for coordinating the development of the data analysis tools for Swift data. The BAT instrument team and the Italian Swift Archive Center will develop data analysis tools for the BAT and XRT data respectively. The Swift Science Center is responsible for developing the UVOT tools.

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What are the Swift mission technical details?
  • Launch Date: November 20th, 2004
  • Prime Mission Duration: 2 years
  • Launcher: Delta II (7320)
  • Orbit: LEO 600 km circular
  • Orbital Life: 7 years
  • Inclination: 22 degrees
  • Dimensions:18.5 feet tall x 17.75 feet wide
  • Spacecraft Partner: Spectrum Astro
  • Peak Slew Rate: 50 degrees in < 75 seconds
  • Arrival: Within 3 arcmin of target
  • Operations and Pointing: Autonomous
  • Uplink/Downlink: Dual Path, 2 kbps GRB alert downlink and uplink real-time using TDRSS MA link, 2.25 Mbps data rat for store and dump using Malindi-ASI seven orbits per day

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What are the specs on the Burst Alert System?
  • Aperture: Coded Mask
  • Detecting Area: 5200 cm2
  • Detector: CdZnTe
  • Detector Operation: Photon Counting
  • Field of View: 1.4 sr (partially coded)
  • Detection Elements: 256 modules of 128 elements
  • Detector Size: 4mm x 4mm x 2mm
  • Telescope PSF: 17 arcminutes
  • Energy Range: 15-150 keV

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What are the specs on the X-Ray telescope?
  • Telescope: Wolter I
  • Detector: EEV CCD-22, 600 x 600 pixels
  • Effective Area: 110 cm2 at 1.5 keV
  • Detector Operation: Photon Counting, Integrated Imaging, and Rapid Timing
  • Field of View: 23.6 x 23.6 arcminutes
  • Detection Element: 40 x 40 micron pixels
  • Pixel Scale: 2.36 arcsec/pixel
  • Telescope PSF: 18 arcsec HPD at 1.5 keV
  • Energy Range: 0.2-10 keV
  • Sensitivity: 4 x 10-14 ergs cm-2 s-1 in 104 sec for known sources
                      1 x 10-13 ergs cm-2 s-1 in 104 sec for blind searches

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What are the specs on the Ultraviolate/Optical telescope?
  • Telescope: Modified Ritchey-ChrŽtien
  • Aperture: 30 cm diameter
  • F-number: 12.7
  • Detector: Intensified CCD
  • Detector Operation: Photon Counting
  • Field of View: 17 x 17 arcminutes
  • Detection Element: 2048 x 2048 pixels
  • Telescope PSF: 0.9 arcsec at 350 nm
  • Location Accuracy: 0.3 arcseconds
  • Wavelength Range: 170 nm - 650 nm
  • Fliters: 7
  • Sensitivity: B = 22.3 in white light in 1000 sec
  • Pixel Scale: 0.502 arcseconds
  • Bright Limit: v = 7 mag
  • Camera Speed: 11 ms

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What is the timeline once a GRB is detected?
  • 0 s: GRB detection
  • 20 s: Slew Begins/BAT approximate location distributed
  • 50 s: GRB acquired
  • 70 s: XRT location distributed
  • 240 s: UVOT finding chart distributed
  • 300 s: XRT light curve distributed
  • 1200 s: XRT spectrum distributed
  • ~ 60,000 s: All automated observations complete (20,000 sec exposure)

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How was the Swift Observatory put into orbit and what was the cost of this mission?
Swift was launched into orbit using a Delta 2 rocket that had 2 stages and 3 rocket boosters. The total cost was about $250 million, including international participation from the UK and Italy.

- Written by Lynn Cominsky, Swift E/PO Lead

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Who is responsible for or had the idea for the swift telescope? Where is it now? What's its purpose to scientists what are they trying to find out with it? and how is it going to get to were it is going or how did it get to were it was going?
Swift was proposed by Neil Gehrels and a team from Goddard Space Flight Center. Work began in 1997 to formulate the mission in response to an upcoming opportunity for MIDEX satellites - Medium-sized Explorers, which was announced in 1998. In 1999, Swift was chosen for a Phase A study, as one of five missions for possible flight opportunities. Later that same year, Swift was one of two selected for flight. It was launched into orbit on 11/20/04. It is in a circular orbit, about 600 km above the Earth, and about 20 degrees inclination to the Earth's equator. It was launched using a Delta rocket, from Cape Canaveral Air Force Station, in Florida. Its purpose is to study gamma-ray bursts, the most powerful explosions seen in the Universe today. A few times per day, somewhere in the Universe, a gamma-ray burst occurs. These bursts are believed to signal the birth of black holes. Swift's mission is to study these bursts, and try to understand the nature of these mysterious explosions.

- Written by Lynn Cominsky, Swift E/PO Lead

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What is the distance of the Swift satellite from the equator?
Swift was launched on an orbit that is tilted by 20 degrees to the Earth's equator. That means it can swing 20 degrees north or south of the Equator, which translates to about 1300 miles north or south of the Equator. This is a rather low inclination orbit for a satellite launched from Florida, which means that Swift never gets high enough above the horizon to see for most people in the United States.

- Written by Phil Plait, Swift Education Resource Director

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Questions about Swift science

Can a gamma-ray destroy the earth?
I think what you mean is a "gamma-ray burst", and not just a gamma ray. Gamma rays are a form of light, like the light we see, except with millions or even billions of times the energy. It takes a very powerful event to create gamma rays.

A gamma-ray burst (or GRB) is just such an event! It's a huge explosion in space, and scientists think they occur when either a very massive star explodes, or two ultra-dense neutron stars collide. Either way, we think a GRB signals the birth of a black hole.

Every GRB ever seen (and we've seen almost 3000 of them) has been very, very far away-- hundreds of millions to billions of light years distant. At those extreme distances, they can't hurt us.

But if one were close, then yes, it could damage the Earth, or even destroy it totally! But it would have to be very close, probably inside our own Milky Way Galaxy. In any one galaxy, GRBs are extremely rare, and we don't know of any stars that might form one anytime soon (like, in the next several million years). So we're probably safe.

Some scientists think that in the distant past, a nearby GRB did cause a mass extinction on Earth-- the Ordovician event, which was 440 million years ago. About 70% of all species on Earth were wiped out, and no one is really sure what caused it. A GRB is a possibility, but it has not been conclusively proved. You can read more about that on this Kansas University website.

So the answer to your question is technically "yes", but I wouldn't let it cause you to lose any sleep!

- Written by Phil Plait, Swift Education Resource Director

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What's the impact of Stephen Hawking on these and related fields of interest?
Stephen Hawking was catapulted into physics superstardom when he predicted that black holes might actually decay with time. The effect is very complicated, involving the very different fields of General Relativity and Quantum Mechanics.

Einstein's Theory of General Relativity can be used to model the effects of the intense gravity near a black hole. Scientists had been using relativity to model black holes for decades before Hawking. Hawking, however, added quantum mechanics to the mix, and predicted that black holes can actually emit particles, which is the opposite of what people expected! After all, black holes are known for eating down matter, not emitting it. Still, the effect means that over time, black holes lose mass, and the rate they emit depends on the mass of the black hole. A "regular" black hole, like the kind made when a massive star explodes, might live for 10^67 years or more, far longer than the age of the Universe (which is about 10^10 years). But a tiny black hole, one with the mass of, say, a mountain, would decay in only a few billion years. If such a tiny black hole, sometimes called a "quantum black hole", were created in the Big Bang, then it would be in its final stages of decay right now. In the last millisecond, it would emit a huge flash of high energy particles and light.

These are different than the gamma-ray bursts Swift detects, in that normal GRBs happen when black holes are born, not when they die. Is it possible to detect such a flash from a dying black hole? I don't think anyone knows for sure, and no one even knows if quantum black holes exist! But if one is detected, it will confirm Dr. Hawking's conjectures and place him firmly in the same pantheon as Newton and Einstein.

- Written by Lynn Cominsky, Swift E/PO Lead

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Can you explain to me the connect between an electromagnet and the electromagnetic spectrum?
Magnetism and electricity are related-- they're like two sides of the same coin! One way a magnetic field can be made is by a *changing* electric field, and vice-versa. Both magnetism and electricity can be generated by moving electrons.

Imagine a single electron moving at a constant speed in a straight line. It makes an electric field, but that field is constant-- it doesn't change. So no magnetic field is made.

But now imagine an oscillating electron--one moving back and forth. The electric current makes an electric field, as before, but this time that field is changing, because the speed of the electron is changing. This makes a magnetic field. But that magnetic field also changes with time, because the *current* is changing as the speed of the electron changes. That change in the magnetic field sets up a changing electric field. And since there is an oscillation going on, you can think of the magnetic and electric fields making each other! The changing current makes the magnetic field, which changes, creating an electric field, which changes, creating a magnetic field, and 'round and 'round we go.

They self-sustain, and what you get is an electromagnetic wave. The words "electromagnet" and "electromagnetic wave" refer to the fact that in both cases electricity and magnetism are working together to cause the phenomena. According to the laws of physics, such a wave must travel at the speed of light, and in fact this wave *is* light. That's why we call light an electromagnetic wave.

A good place to read about this is Nick Strobel's Astronomy Notes web site: http://www.astronomynotes.com/light/s2.htm (he also has some nice graphics to go along with his explanation), and he continues the discussion here: http://www.astronomynotes.com/light/s3.htm.

- Written by Phil Plait, Swift Education Resource Director

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Is there any reason why the explanation for gamma-ray bursts can not include all three current hypotheses?
There is no reason why the explanation for GRBs could not include all three scenarios listed - in fact, there could be many more than three causes for GRBs. The reason that there are two popular scenarios is that observationally GRBs appear to be divided into two classes: those shorter than 2 seconds, and those longer than 2 seconds. If this classification scheme is correct, then it would follow that there are two different causes for the bursts. However, there are other properties of the bursts which differ and could lead to alternative explanations. The jury is still out as to the classification scheme and the associated mechanisms, especially for the shorter class of bursts.

- Written by Lynn Cominsky, Swift E/PO Lead

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Will we be able to 'see' images of gamma-ray bursts on the Swift site?
Yes, you will be able to see Swift images from the site. Right now the best place to find these images is in the tab called "Swift Results" and "quick look data" (these are both links off of the main swift pages.) We also have the grb.sonoma.edu page which is great for everyone. This site too will also have the images taken by swift of the various bursts. Of course, we are still in the check out phase for Swift so everything is not yet up and running. We also don't have many images taken yet.

- Written by Sarah Silva, Swift E/PO Program Manager

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Has anyone ever tried to follow up gamma-ray burst events in the radio waves?
Many radio observations have been done of the afterglows of GRBs. The radio emission comes from the same shock that gives rise to the optical and X-ray emission but the radio reaches peak brightness 5-10 days after the burst. This "afterglow" emission is associated with the synchrotron emission from shocked electrons in the jet. (Synchrotron emission is light emitted due to the acceleration of the electrons by strong magnetic fields.) At early times, the shocked fireball is too small to produce significant radio emission. It is only when the shock expands that the radio gets bright enough to detect.

- Written by Dale Frail, NRAO

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Are there any radio telescopes available in the world with the capability of quickly focusing on such an event?
Yes, despite the fact that we expect the emission to be weak, there have been several experiments to detect "prompt" radio emission. None of these have been successful but we keep trying. The most sensitive telescopes in the world first start detecting the radio afterglows about 24 hrs after a gamma-ray burst.

- Written by Dale Frail, NRAO

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What information could potentially be gleaned by radio wave measurements of a real time gamma-ray burst?
If you could detect prompt radio emission from a gamma-ray burst there are several things you could do. The most important would be to measure the delay in the arrival of the radio signal. A delay is expected because the signal gets to us only after propagating through a large amount of ionized gas between us and the source. Detecting prompt radio emission would be a unique probe of the gas density of the early Universe.

- Written by Dale Frail, NRAO

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Did I just see a gamma-ray burst? There was a brilliant light in the Northern section of sky, and then (a second later) another brilliant flash of light a little lower than before but at a declining angle. After second flash, nothing more occurred. No trail like a falling star or comet would make.
A common event often mistaken by people in the sky to be a Gamma-Ray burst is an Iridium Flare. If you visit this link http://www.heavens-above.com, then put in your latitude and longitude, you will be able to see if there were any of these flares reported during this time.

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A service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Andy Ptak (Director), within the Astrophysics Science Division (ASD) at NASA/GSFC