Dr_Ronald_Blom: I'm very pleased to be here and to be able to chat with you all. Today has been a very exciting day after years of planning. We are finally in space and hopefully soon we will begin acquiring data and will be able to generate a high resolution topographic map of the world.
guest-Dick: Dr. Bloom, When will you start receiving data?
Dr_Ronald_Blom: They will be turning the radar on very soon. I don't know the precise time. The first data to be processed will be processed late tonight. So, we will know the health of the entire system probably by midnight PT.
guest-digger: What is the principal goal of the Shuttle Radar Topography Mission?
Dr_Ronald_Blom: The principal goal is to make a globally consistent topographic data base of the land surfaces of the earth. Such a thing does not exist now. Topographic data is one of the most basic data sets one can imagine and it's truly remarkable that even today we do not have good topographic data for much of the earth. Topographic data is an essential input for many disciplines, including agriculture, hydrology, concern about flooding, even archeology.
guest-MarcoB: What can this device do that other space-based radar satellites can't do?
Dr_Ronald_Blom: Because of the unique configuration of SRTM with the second
antenna on the end of a 60-meter long mast, we are able to collect topographic data in a single pass. No other radar satellite can do that and multiple-pass topographic data is subject to a number of errors and is much more difficult
to process. So, despite several years of satellite radars, no one has developed a global topographic data set from them. In fact, only limited topographic data has been generated from them.
guest-Yemen: Do any by-products of the mission that stand out?
Dr_Ronald_Blom: Yes. The truly remarkable thing (and it's really a by-product of the mission) is that we will have a radar image of the entire land surfaces of the planet from this one 10-day mission. So we are getting a snapshot of the whole planet in a very short period of time. There's nothing else like that. What makes this so interesting is that in 100 years, we will probably have better topographic data than SRTM will provide. However, a picture of the earth from a 10-day period in year 2000 will always be a unique resource for detecting global changes.
dragonmasterryu: Why do people want to know so much about the lost city? Why don't they just leave ancient things alone?
Dr_Ronald_Blom: It is important to understand our past so that we can do a better job of managing our future. A number of civilizations and perhaps even us, have, through bad management of their resources, met their demise. We can learn from studying these things.
guest-Darth: What sets this mission's radar imaging apart from more traditional satellite photos of the planet?
Dr_Ronald_Blom: The thing that sets it apart from satellite photos such as those provided by Landsat is that Landsat and other optical wavelength sensors cannot see through clouds or in the dark, northern latitudes. So, it's not possible to get consistent images from them. In addition, this mission is different than other radar missions because of the concentrated effort in producing a global data set over a very short period of time. This will provide a basic data set that is otherwise not available. Also, the topographic data that we derive will greatly enhance the value of other satellite images because topographic data is what turns the satellite picture into a place, because you can now make a 3-D picture of the place using the satellite image and the topographic data.
Asterzix: Who takes the fall when software goes bad?
Dr_Ronald_Blom: Not me! <g> The people who are responsible for the software will take a lot of flak if there is a mistake. However, it's been thoroughly tested.
guest-Frontier: How will these snapshots of the planet benefit humanity in the coming years?
Dr_Ronald_Blom: There's two things that SRTM will provide that will be very useful in the future. The first is this global image acquired over a relatively short period of time, that I mentioned. That will be a basic data set that people will compare things to in the future. The second thing is the unique capability of providing the topographic data which is so essential for many other disciplines.
guest-Digerido: Why didn't researchers use this radar mapping earlier for things like archeology?
Dr_Ronald_Blom: It's only recently that satellite images and other new technology have been applied to archeology. There are several reasons, including the expense of the data, the relative lack of computer power to process them, and general unfamiliarity with the technology in the archeological community. All of these things are now changing and there are a number of archeological applications which use remote sensing as one of the tools for exploration.
guest-LtLeah: How can it map when the earth has clouds covering it?
Dr_Ronald_Blom: Radar wavelengths are not reflected by clouds. In fact, clouds are almost complete transparent to the radar just like your car windshield is transparent at visible wavelengths of light.
wesinla: What city was lost for 1600 years?
Dr_Ronald_Blom: The lost city of Ubar met with a calamity about 300 A.D. It was really just a fort, not a city, and thisfort in the desert was used to organize camel caravans to transport frankincense. The city was lost because the fortress collapsed into a sinkhole and the site was abandoned. Coincidentally, the price of frankincense in the ancient world dropped dramatically as the Roman empire became Christian and that is probably why the site was not re-occupied.
BlessYu: What and where is Ubar?
Dr_Ronald_Blom: Ubar is in the country of Oman, which is a country on the southeastern corner of the Arabian peninsula, so it is south of Saudi Arabia. Ubar was a legendary city that controlled the desert trade routes for frankincense which was a very valuable commodity in the ancient world. If you look on a modern map, the site is at the location of Shisur.
guest-alexferfa: What do I need and where should I go to become an astronaut? I am 18 year old and since I was 8 I have been thinking to become an astronaut. I am from Venezuela and I am living in Canada and looking for an opportunity to become an astronaut, but I don't know if I am in the right place.
Dr_Ronald_Blom: I'm not sure how to become an astronaut, but I would recommend looking on the NASA websites. I do know that NASA's main website has lots of information for students and that might help lead you in the right direction.
guest-LtLeah: What about looking for the lost city of Atlantis? Can they find it from space?
Dr_Ronald_Blom: The Atlantis legends were almost certainly derived from the explosive volcanic eruption of Santorini and the collapse of the Minoan civilization in the Mediterrean Sea. So, in a sense, Atlantis is already known. Pliny, the Roman historian, says that Atlantis existed outside of the gates of Gibraltar because he was unaware of Atlantis' true size.
guest-allison: Have you been to the lost city?
Dr_Ronald_Blom: Yes, I was there twice in the early 1990's as part of our exploration for the lost city and also reconnaissance into the ancient desert frankincense trader routes. The site has been excavated by Professor Zarins and there is some material being published now. There is also a PBS "Nova" documentary called "Lost City in Arabia," which airs occasionally, and there is some information on the PBS website about the documentary and also the site. We have continued exploring in southern Arabia for other sites because Ubar was only one of several sites. In fact, Roman records indicate there were eight desert outposts on the frankincense trade route, and we are now looking for the others. We have made two trips to Yemen, which is the country to the west of Oman, to search for these other desert outposts.
FLYGUY391: Will the data collected be used in updating current quad maps of the U.S. that are available to the public?
Dr_Ronald_Blom: Most of the USGS quadrangle maps are already of similar resolution and quality to the SRTM data. Only the older lower quality ones will be updated by SRTM data to my knowledge. SRTM's main benefit is mapping parts of the world that are not so well-mapped as the United States. Also, you should know that the USGS topos are available digitally free online from the U.S. geological website.
guest-haarbu: Will you make a Viewmaster reel from the 3D images?
Dr_Ronald_Blom: We had not thought of such, but that is a great idea.
Test_Probe: What sort of resolution do you get from the equipment?
Dr_Ronald_Blom: When the data are processed, the best data will have one elevation measurement for every 30-meter square on the ground, and that elevation measurement will have an absolute accuracy of better than 16 meters and a relative accuracy of better than 10 meters.
BlessYu: What will happen to the satellite once the pictures are taken? Will there be another use for it?
Dr_Ronald_Blom: The SRTM equipment will be placed in storage for a possible return flight. A return flight would allow us to pick up data for any areas missed because of problems on this flight and, in addition, if we were to collect a second global data set, we would be able to improve the accuracy of our topographic maps. However, at the present time, there are no specific plans to re-fly the equipment. The main part of the instrument is, in fact, the SIR-C instrument, which was flown twice in 1994.
Test_Probe: How small of an area on earth can this SRTM resolve?
Dr_Ronald_Blom: The resolution, or pixel size, is 30 meters (about 95 feet).
guest-Chaffe: Why doesn't NASA make a satellite with the same technical image equipment so we can study changes, as well as adding new tech every few years to 'upgrade' the system?
Dr_Ronald_Blom: We would very much like to fly a satellite mission dedicated to radar interferometry measurements, which is the key technology to making the topographic maps. If we could fly a satellite that would be up all the time, we would be able to map tiny changes on the surface of the earth using this same technology. So, we would very much like to fly a satellite.
__GypsyRose__: What else can this radar see and do to help everyone else?
Dr_Ronald_Blom: Global topographic data base has so many applications that it will be a great benefit in many disciplines. In particular, there are no good topographic maps of the rain forests, such as in Africa or Eastern Asia. The potential includes being able to map things like mountain glaciers to detect changes in the ice volume which are sensitive indicators of climate change. We may even be able to improve maps used by boaters navigating in coastal waters. Some areas are not well-mapped because of cloud cover and we may be able to improve hiking maps. The range of applications is very large.
guest-iMacbeth: Is it true that researchers stumbled upon this use of radar images from space largely by accident?
Dr_Ronald_Blom: No. It was known for a long time that theoretically you could use interferometry to determine topography using radar data. As a practical matter, it is a very difficult problem and it was only about 20 years ago here at JPL, where we experimented with some old radar data and through great effort, that we showed that in fact it was possible to do this. The details of keeping track of the signals and the exact position of the antenna and the exact position of the orbiter are truly daunting, so making these maps is actually a very difficult task that has only become practical over the last very few years.
guest-ChrisLee: What was it like to move ffrom looking at the satellite image of Oman to actually being there?
Dr_Ronald_Blom: I'm always surprised at the things you can see in a satellite image, and I am also always surprised by the landscape when I actually get there. I have been to many places where we have both satellite images and maps, and I am always surprised when I get there on the ground. In the particular case of Oman, it is hard to describe how extremely hot and barren the landscape is. You have to experience it.
guest-dukie: Will you be able to note changes in the coastlines?
Dr_Ronald_Blom: The SRTM data will provide us with the details of the coastlines during this 10-day mission. In order to detect changes, we will have to fly it again or else use other data to compare it with over time. An interesting thing about the coastal maps that will be made using SRTM is that we have to think about the tides at each location at the precise time the SRTM data were acquired, so there is an additional detail that must be considered when producing the maps.
guest-crappiejig: Doctor, will the radar penetrate water, allowing a image of the ocean floor, or will it reflect off of the water?
Dr_Ronald_Blom: Radar does not penetrate water. Radar reflects off the very upper surface, so the radar will not directly image the ocean floor and, in fact, for SRTM, the radar will be shut off over most of the ocean. However, you are probably referring to images showing the ocean floor topography that have been made from space. These are made in a little different fashion. Because the surface of the ocean actually goes up and down in a reflection of the bottom topography because of gravity, this allows you to make topographic maps of the ocean bottom by very precisely measuring the height of the sea surface. There are other satellites that provide such data.
cthru12: Is it true that the government will use technology such as this used in warfare and on U.S. citizens?
Dr_Ronald_Blom: The U.S. government already has better topographic maps than SRTM will provide for any area of their potential interest. This data is much more useful for more mundane uses. As far as using the data on U.S. citizens, we already have excellent digital topographic data of the United States which is available free online and you can use it next time you go hiking.
Test_Probe: Could this satellite find use in a Mars orbital plane?
Dr_Ronald_Blom: The same technology could be used to produce a topographic map of Mars. However, there is a different technology on the current Mars orbiter which, because Mars has so few clouds, uses a laser to measure height very precisely. We are accumulating a fine topographic map of Mars using this type of data.
BlessYu: Does this mission have anything to do with the upcoming planetary alignment May 5, 2000?
Dr_Ronald_Blom: No.
__GypsyRose__: Can the radar see or foretell any global disasters?
Dr_Ronald_Blom: The radar will be a significant aide in mapping areas prone to disasters, such as from flooding or also volcanic eruptions and things like that. Topographic data, for example, is essential to mapping the extent of flooding during various weather events. So again, the topographic data is a basic data set that can be used in disaster planning and even response. But it cannot directly foretell disasters, obviously.
cthru12: How much is this costing?
Dr_Ronald_Blom: The real answer is I'm not sure, but I believe the direct costs are about $200 million. However, it was planned to produce a similar topographic data set for the world using more conventional technology, and the estimates for that job were in the billions. It would have taken decades to accomplish because of cloud cover and data processing bottlenecks.
guest-Chaffe: It is amazing how much we are advanced in technology today. Why wasn't this kind of project done sooner? And how long has this project been going on?
Dr_Ronald_Blom: The ability to fly SRTM grew directly out of the SIR-C mission, which was flown in 1984. That's what gave us most of the hardware. And as far as doing it sooner, given the combination of the technology and the politics, it was not possible to accomplish this before now. However, various science panels have been recommending acquisition of a global topographic data base for at least 15 years that I am aware of. But again, because of the technology only recently all coming together, it hasn't been possible until now.
BOOMSHOT: Who do you feel is the most supportive presidential candidate from either party when it comes to space exploration?
Dr_Ronald_Blom: I have not paid much attention to the candidates' views on space exploration, unfortunately. My only comment at this stage would be that Vice President Gore has been a strong supporter of the space program in general.
However, there may be other candidates with stronger support that I'm not aware of.
nick_zachbrown: Does radar track UFO's?
Dr_Ronald_Blom: There have been reports of radar tracking things that have been identified as UFO's. However, I'm personally familiar with incidents where the radar tells you something is in one place and, in fact, it is somewhere else. The funniest thing I can think of is the radar image of a moving train in which the radar clearly shows the train tracks but because the train is moving, it is Doppler-shifted off of the tracks and the train is in a farmer's field several meters off the track. So, one has to be careful when interpreting radar data to think about all of the possibilities. I would also anticipate that any UFO's would probably be quite stealthy and not reflect radar waves to begin with.
Test_Probe: Can this radar look below the soil, say a few centimeters?
Dr_Ronald_Blom: Radar can, under very restricted environmental conditions, penetrate dry soil or dry sand. The best example that I am aware of is sand in the Sahara, which is one of the driest places on earth. Radar was able to image features beneath two meters (over six feet) of sand. The conditions that allow this are very rare, however. And even in the Mojave Desert of California we have only seen a very few places where radar was able to see something subsurface. That is because the Mojave is a swamp compared to the Sahara. So, radar can see through a thin cover of very dry material, but if it is wet at all it will reflect off the surface.
guest-mandible: What inspired you to get into this area of science initially? What education and experience is necessary for someone to work at the Jet Propulsion Lab? Any internships...hmmm? <g>
Dr_Ronald_Blom: My training is actually in geology and one of the main things that a geologist does is make maps. Years ago I was fascinated by the pictures from space and I realized that they could be a very good tool to help in making maps that might be of interest to geologists. In fact, I came to JPL because of the access to the computer power and expertise that used to be required to process satellite images from space. Interestingly, the power of computers available to anyone today has reached the point that I do my image processing on a Macintosh. Meanwhile, as far as education, I have a Ph.D. from the University of California at Santa Barbara. The geology department there has always had people interested in the big picture such as you can get from space. These days, much research using space-based data is done in the universities and there are any number of universities that one could go do to earn advanced degrees using space-based data. You might go snooping on the web. Universities that occur to me include Brown University in Rhode Island, Washington University in St. Louis, Washington University in Seattle, University of Nevada at Reno. University of Arizona, Arizona State University, and I have probably forgotten someone who will be mad at me for forgetting them. <g>
guest-Trekker: Where else do you think this technique might be used? Are archaeologists bugging you to point the satellites at some other spots? Where?
Dr_Ronald_Blom: With the success of the work at Ubar, in fact, a number of archeologists are making use of satellites in various areas. Work that I am aware of include Petra in Jordan, which was featured in the "Indiana Jones" movies, by the way. Also, Ankor Wat in Cambodia, where some excellent work has been done. Also, the Mayan civilizations in Central America and Southern Mexico. Personally, I am working on a project in eastern China, where we are applying various satellite images to look for the remains of an early Chinese civilization called Shang. Another interesting site I am working on is a civil war site in Saltville, Virginia, where the confederacy got most of its salt. It was a strategic target for the Union. The site is interesting because historical accounts indicate that it was much larger than the present known extent of it and we are having some luck using aircraft and satellite images to map the area. I anticipate that with the increasing power of computers, the increasing availability of this kind of data, and the decreasing cost of the data that more and more applications will be found. I think this is really important because we are destroying our collective cultural heritage at a faster rate than we are discovering or documenting it, so I have great hopes that this type of data will help us in the future.
Space.com: Dr. Blom, thank you for being with us this evening and for this fascinating information! Do you have any final thoughts for our audience?
Dr_Ronald_Blom: I think it's important for people to know that there are lots of things to be discovered out there and there are many new tools that can help one in these kinds of searches. What's most important is to be a true scholar and be sure that all of your information is good. Another important thing is to use experts from many different fields. In thinking about the Ubar experience, we had an historian, an archeologist, a documentary movie producer and a space cadet - namely me - and it would not have worked without all of us. None of us could have done it on our own.
Space.com: Thank you for very much for joining Dr. Ronald Blom here at Space.com's live chat. To learn more about the Lost City of Ubar check out our STS-99 Mission special report. This event was presented by Space.com and produced by Talk City, Inc. Copyright 2000. All rights reserved.
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