Jim Green: A lot of people are familiar with the concept of an antenna from a radio or TV set, for which they receive a signal. But when we take a look at a spacecraft, we see all type of different antennas. Whats their primary function?
Nacer Chahat: Yes, so, the principle is the very same. Many of the interaction antennas will be the normal dishes that we see.
Jim Green: You know a great deal of the antennas that you use, you utilize for what we call remote picking up. Whats that truly mean?
Nacer Chahat: So, remote sensing permits us to get something from afar therefore were using radio frequency to transfer pulses. These pulses are reflecting back from the surface of what we wish to study, and then were processing this data to make conclusions.
Jim Green: Yeah, thats whatever from having the chance to bounce radio waves off surfaces to even permeate those radio waves into surfaces like, like the ice caps or even the Sahara Desert.
Nacer Chahat Yeah, which likewise allows us to get pictures of things we can not see. For example if the weather condition is bad and Earth is completely covered with clouds, we can still see whats happening under them.
Nacer Chahat of NASAs Jet Propulsion Laboratory with a design of the Ingenuity helicopter. Credit: NASA/JPL-Caltech
Jim Green: Well, you know, interaction with our surface possessions on Mars is type of complicated. You understand, when we landed Curiosity, I dont see it carrying a big truck with a big meal behind it. How do we interact back and forth with, with our surface area possessions, like InSight, like Perseverance, like Curiosity?
Nacer Chahat: Yes, so we have 2 principles to do so. The very first one is to interact with the orbiter. So we have orbiters around Mars which we can, they are committed for science, however for a vital occasion like that, we can utilize them to pass on the data to Earth. And we also have on these landers and rover, high gain antennas that allow us to communicate straight with Earth but at lower information rate. Its truly a trade-off. When, when we need to be using the orbiter or when we should be utilizing the high gain antenna. The majority of the time, we wind up using the orbiter since it permits us to send the science much faster. Those are the factors and many of the Mars objective have constantly worked this method. So we transmit the information to the orbit and the orbiter transmits back to the to the Deep Space Network in the world.
Jim Green: Yeah, that sounds complicated, however it provides a facilities that permits any asset thats on the surface to be able to be passed on through our orbiting satellites. Its truly an amazing time in this specific field.
Jim Green: You know when the InSight lander showed up arrived on Mars in November 2018 it carried with a 2 CubeSats and we call those CubeSats “MarCO.” What were they expected to be doing and how crucial was communication for them?
Nacer Chahat: Yeah so MarCO was actually among my first tasks, and when I joined JPL the former director of the lab, Charles Elachi, challenged the laboratory to find a method to do real time communication during the financing of InSight. With the existing orbiter we were able to collect all the info from InSight during the landing However due to the fact that of the alignment of the orbiter, we could not get the information right away.
Nacer Chahat: So the function of these two CubeSats was actually to receive information from the lander, InSight, and transmit these information in real time so the, the primary difficulty was to be able from these extremely, extremely small satellites which are the size of a shoebox, being able to transfer at the very same information rate which was roughly around 8 kilobits per second. We had to discover a way to fold the antenna and deploy it.
Nacer Chahat: When we experienced the landing of InSight we were all thrilled due to the fact that for those who really follow the landing you need to keep in mind when they were saying oh we are now 100 meter 90 meter 20 meter and all the enjoyment was showing up all I had in mind was oh thats my antenna whos transferring all these information and after that he landed we exploded with delight and we lastly received these very first images from InSight on the surface of Mars which also got passed on utilizing the MarCO antenna.
Nacer Chahat: If we did not have the CubeSats we would have needed to wait more than two hours after that.
Jim Green: Wow.
Nacer Chahat: Because the orbiter was not on the line of sight.
Nacer Chahat So, thats such a remarkable achievement that weve had the ability to do whichs truly whats beautiful about working at NASA is that were able to do things that nobody has actually done in the past.
Jim Green: Yeah i keep in mind that time I was head of planetary science and it was really fascinating and i was just pleased that the MarCO spacecraft worked.
Jim Green: And in truth, it was actually nailbiting for the simple reason that we were having problems with among the MarCO spacecraft really close to the encounter time. Do you keep in mind that? And what took place?
Nacer Chahat: I do, I do, and we were extremely concerned about that. So among them really rebooted? Like, I believe it was a few hours prior to possibly a day in the past, I dont remember precisely. So we were worried that one of the CubeSats would not have the ability to associate with data. However after it restarted, it entered safe mode and rebooted in a nominal mode. And they both successfully related the data.
Jim Green: Well, you understand, were flying a helicopter on Mars for the very first time. And we call that Ingenuity. Did you get involved in that? And whats your function?
Nacer Chahat: When I saw the very first flight, I couldnt think but help of all these hours spent working really tough to solve technical problems. All these individuals working on delivering hardware that you do not necessarily see on television. This achievement is absolutely historic and I more than happy I got to contribute.
Nacer Chahat: My contribution was with the telecommunication subsystem, to make sure that the rover can send commands to the helicopter, and the helicopter can send images or telemetry back to the rover. So, I worked on the antenna style and also dealt with the system engineering.
Jim Green: Wow, that sounds actually difficult because this is a really little vehicle. Whats that antenna appear like? I do not keep in mind seeing it. Does it stick out? Or is it part of … does it go up to the leading or, wheres it at?
Nacer Chahat: Yeah On the top of the helicopter, there is a solar panel, which enables us to recharge our battery. And we decided to locate the antenna on this surface, due to the fact that this is what provided the largest location to utilize as a reflective surface area. This is the simplest type of antenna that you can ever utilize. This is called a monopole. Monopole is generally a single wire, which is resonant at the frequency of operation, and situated on top of a reflective surface area. And the reflective surface area in this case is the solar range.
Nacer Chahat: This wire allows us to operate at the frequency of interest. Thats the factor why we use such an antenna.
Nacer Chahat: Its extremely little its about 5 to 6 centimeter which is essentially a quarter wavelength or the frequency of operation.
Jim Green: Yeah, that makes a lot of sense. I suggest, yeah, you move the copter and it comes back down. And its not necessarily in that same orientation.
Nacer Chahat: Exactly.
Jim Green: So you wish to transmit. It sounds …
Nacer Chahat: Yeah.
Jim Green: … like though the Ingenuity interaction is just with, with Perseverance, and after that its up to Perseverance to package that information and after that send it approximately an orbiter which then relays it back to Earth.
Nacer Chahat: Thats, thats exactly it. And the reason is extremely basic is that certainly with such a small helicopter, we will not be able to communicate directly to the orbiter, and even less with Earth. The helicopter is also has to, to, to stay away from the rover itself because the rover needs to be totally safe.
Jim Green: Wow, that sounds actually fun. Another thing that NASA likes to do is think about objectives that are in the future. And how does that have to work?
Nacer Chahat: The initial idea of the Europa lander concept was to send out an orbiter too, together with the lander, and the orbiter will have interaction telecommunication abilities to communicate the information back to Earth. Nevertheless, doing so would have been cost-prohibitive. We were asked extremely quickly to revise the principle to minimize the cost so that this mission could sooner or later be possible.
Nacer Chahat: And the only way to do so was to interact straight with earth so that we dont have to have an orbiter. So, to do that, the conclusion that was that we needed an antenna with an effectiveness of more than 80%, which to offer you an idea, has actually never ever done prior to. All of the Mars rover or lander, they have effectiveness of less than 45%, approximately. But the lander has additional restraints. The antenna required to be flat, it required to endure the environment, and very high radiation of Europa. And for those reason, people thought it was simply not possible to do so.
Nacer Chahat: So we developed an antenna style that fulfills all these requirements and attained the efficiency we completely checked be something to the environment of Europa, to qualify the something out for a possible Europa lander mission in the future. And so now were in an extremely, extremely, extremely great shape, since we know that this Europa objective concept is possible. We have all the technology that are required to do that, because NASA supported us to develop all of these innovations.
Jim Green: Yeah, thats truly terrific. Now coming back to the Earth, your present job is on SWOT, which is the Surface Water and Ocean Topography Mission.
Nacer Chahat: No, we are right now we are in combination and testing, what we call INT. The function of SWOT is to measure the surface area topology of the ocean, however also the water surface for the very first time. And so were really, extremely delighted to see this objective moving along and getting really prepared to fly.
Jim Green: So whats the new improvement in antenna technologies?
Nacer Chahat: Every single objective have various requirements. We tend to develop a brand-new antenna every single time. I would say that the holy grail of the antenna, from my perspective, would be to create an antenna that could be obtained every objective to satisfy any requirements. So clearly, thats, thats nearly impossible to do so. However for interaction, thats possible, you could come up with an antenna that might shave the beam in any way we desire for a provided aperture. And thats what Im working on, on my research study science, to achieve such a thing.
Jim Green: Sounds fantastic.
Jim Green: Nacer, I constantly like to ask my visitors to tell me what was that occasion that person, location or thing that got them so fired up about being the engineer they are today. And I call that occasion a gravity help. Nacer, what was your gravity help?
Nacer Chahat: The researchers that I respected the most is Marie Curie, who was also from the exact same country that I am from, from France. Truly, what I like about my inquiry is her commitment for work. Since she in fact offered her life for her work, and I think no one was as committed as her. And the work ethic that she has actually demonstrated is what, what I share the most with Marie Curie.
Nacer Chahat: So but I would, I would state, as well, that its not always an engineer, or a scientist that actually motivated me, in my case. After they moved in France, I was born and raised in France, they actually share this idea of understanding that the education is a present. Thats why I always worked truly, truly tough to do as much as I could and find out as much as I could.
Nacer Chahat: And so I would say that my gravity assist are not engineers or researchers, however actually my parents.
Jim Green: Now, thats a wonderful story. Thank you so much for sharing it with me.
Jim Green: Nacer, thank you a lot for joining me in discussing this great subject.
Nacer Chahat: It was my enjoyment. Its constantly its, its always terrific to share the experience that we have actually provided establishing new technology at JPL. So thank you for having me.
Jim Green: Join me next time as we continue our journey to look under the hood at NASA and see how we do what we do. Im Jim Green and this is your Gravity Assist.
Well hear about it from Nacer Chahat of NASAs Jet Propulsion Laboratory, who works on antenna and telecommunication systems for a range of NASA missions. He chats with NASAs Chief Scientist Jim Green in this episode of the Gravity Assist podcast.
Well hear about it from Nacer Chahat of NASAs Jet Propulsion Laboratory, who works on antenna and telecommunication systems for a range of NASA objectives. Jim Green: Im here with Nacer Chahat, and he is the senior antenna and microwave engineer with NASAs Jet Propulsion Laboratory out in Pasadena, California. Nacer Chahat: When I saw the very first flight, I could not think but assist of all these hours invested working really tough to fix technical issues. Nacer Chahat: So we came up with an antenna style that fulfills all these requirements and attained the effectiveness we totally checked be something to the environment of Europa, to qualify the something out for a possible Europa lander objective in the future. Nacer Chahat: So however I would, I would say, as well, that its not always an engineer, or a researcher that really inspired me, in my case.
Jim Green: NASA flies spacecraft all over the planetary system, and orbits the Earth. How do we interact with them when theyre so far away? Lets discover from a specialist.
Jim Green: Hi, Im Jim Green. And this is a brand-new season of Gravity Assist. Were going to explore the inside workings of NASA in making these wonderful objectives happen.
Jim Green: Im here with Nacer Chahat, and he is the senior antenna and microwave engineer with NASAs Jet Propulsion Laboratory out in Pasadena, California. He has dealt with one of the most important challenges for NASA which is, in designing a spacecraft, how do you make it interact backward and forward with Earth? So welcome to Gravity Assist.
Nacer Chahat: Thank you for having me here.