I need to have articles for the newsletter by Friday April 24 so I can publish the April newsletter. Obviously our normal monthly meeting would be that same Friday, however the meeting is canceled. Jim

Hi Jim, Here’s a short article I found that would be of interest to some: Antennas for Small Satellites (like the CubeSat): Challenges arise when working with smaller CubeSat structures, like the 1U CubeSat. Due to the antenna’s large form factor for low operating frequencies (L band and bellow) they have to be deployable. Deploying these antennas can be realized in two ways. First, with the use of motors a folded or rolled antenna can be deployed when in orbit. A VHF antenna uses this deployment method. The antenna is rolled in the stowed state and straight in the deployed state. It is reinforced with glass fiber epoxy to become elastically stable, both at stowed and deployed states, so that no force is needed to maintain the stowed or deployed states, needing only an mechanical actuator to start the deployment. Second, a wire antenna made from a flexible conductive material can be folded and stowed inside the CubeSat’s structure in a way that it stores strain energy. The antenna is secured with a wire and is released in orbit, regaining its original shape. The wire that holds and releases the antennas is usually a nichrome burn wire that heats up when supplied with a current, cutting a string of fiber that is holding the antenna. This widely used deployment method in CubeSat missions has the disadvantage of being prone to mechanical failure, as the wire can break from the heavy vibrations and forces experienced at launch. If the deployment mechanism fails, the antenna will not deploy and it would be almost impossible to have a communication link with the satellite. This problem was experienced by engineers at Cal Poly on their 3U CubeSat, the ExoCube. Source: https://fenix.tecnico.ulisboa.pt/downloadFile/281870113704695/Dissertation.pdf <https://fenix.tecnico.ulisboa.pt/downloadFile/281870113704695/Dissertation.pdf> Another topic might be some info about an update on this project: Five-Hundred-Meter Aperture Spherical Telescope (FAST) is a Chinese megascience project that aims to build the largest single dish radio telescope in the world. Joe - WA8OGS > On Apr 13, 2020, at 1:29 PM, Jim Bacher via mvus-list <mvus-list@lists.febo.com> wrote: > > I need to have articles for the newsletter by Friday April 24 so I can > publish the April newsletter. > > Obviously our normal monthly meeting would be that same Friday, however the > meeting is canceled. > > Jim > _______________________________________________ > mvus-list mailing list > mvus-list@lists.febo.com > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com

Joe, the FAST telescope is a done deal, pretty much. It went into operation about the time I retired from Arecibo, but has apparently been plagued with essentially mechanical problems with the scheme they use to tug the illuminated region of the dish into a parabolic contour. The idea is that as an object of interest moves across the sky, the feed in use is steered to illuminate the portion of the dish that will form a beam pointed at the object, and this complicated system that lives beneath the dish dynamically tugs that area of the dish into a parabola. So it's beam steering principal is very different from that used at Arecibo. I don't know what the current status is. What I wrote above may by now be stale info. The FAST telescope excels over Arecibo in terms of active aperture (read, sensitivity) and in terms of the total amount of sky it can cover. However, the surface accuracy is not as good as Arecibo's *normal *accuracy, so FAST's upper frequency limit is quite a bit poorer than Arecibo's. Also, as far as I know, FAST has no provision for adding radar transmitters; if true, FAST cannot be used for ionospheric studies or tracking and imaging of planets or asteroids. And, as I understand it, FAST makes no provisions for people to visit the feed house while it's suspended over the dish- now where's the fun in that? Dana On Mon, Apr 13, 2020 at 3:17 PM Joe via mvus-list <mvus-list@lists.febo.com> wrote: > Hi Jim, > > Here’s a short article I found that would be of interest to some: > > Antennas for Small Satellites (like the CubeSat): > Challenges arise when working with smaller CubeSat structures, like the 1U > CubeSat. Due to the antenna’s large form factor for low operating > frequencies (L band and bellow) they have to be deployable. Deploying these > antennas can be realized in two ways. > > First, with the use of motors a folded or rolled antenna can be deployed > when in orbit. A VHF antenna uses this deployment method. The antenna is > rolled in the stowed state and straight in the deployed state. It is > reinforced with glass fiber epoxy to become elastically stable, both at > stowed and deployed states, so that no force is needed to maintain the > stowed or deployed states, needing only an mechanical actuator to start the > deployment. > > Second, a wire antenna made from a flexible conductive material can be > folded and stowed inside the CubeSat’s structure in a way that it stores > strain energy. The antenna is secured with a wire and is released in orbit, > regaining its original shape. > The wire that holds and releases the antennas is usually a nichrome burn > wire that heats up when supplied with a current, cutting a string of fiber > that is holding the antenna. This widely used deployment method in CubeSat > missions has the disadvantage of being prone to mechanical failure, as the > wire can break from the heavy vibrations and forces experienced at launch. > If the deployment mechanism fails, the antenna will not deploy and it would > be almost impossible to have a communication link with the satellite. This > problem was experienced by engineers at Cal Poly on their 3U CubeSat, the > ExoCube. > Source: > https://fenix.tecnico.ulisboa.pt/downloadFile/281870113704695/Dissertation.pdf > < > https://fenix.tecnico.ulisboa.pt/downloadFile/281870113704695/Dissertation.pdf > > > > > Another topic might be some info about an update on this project: > Five-Hundred-Meter Aperture Spherical Telescope (FAST) is a Chinese > megascience project that aims to build the largest single dish radio > telescope in the world. > > Joe - WA8OGS > > > > On Apr 13, 2020, at 1:29 PM, Jim Bacher via mvus-list < > mvus-list@lists.febo.com> wrote: > > > > I need to have articles for the newsletter by Friday April 24 so I can > > publish the April newsletter. > > > > Obviously our normal monthly meeting would be that same Friday, however > the > > meeting is canceled. > > > > Jim > > _______________________________________________ > > mvus-list mailing list > > mvus-list@lists.febo.com > > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com > > _______________________________________________ > mvus-list mailing list > mvus-list@lists.febo.com > http://lists.febo.com/mailman/listinfo/mvus-list_lists.febo.com >