9
$\begingroup$

I can find several descriptions of what the SpinSat satellite was supposed to do. I can find some nice images of it being deployed from the ISS also. But I haven't been so successful in understanding whether the whole mission worked.

Did the Digital Solid State Thrusters successfully spin up the satellite, and then de-spin it again? Was the performance in this demonstration as good as what was anticipated?

Were the spin-up, and especially the de-spin maneuvers performed using real-time attitude and rotation measurements? The electric thrusters are pulsed, so thrust can be metered out in controlled amounts, so conceivably the de-spin could be done as a single maneuver, with the thrusters fired until spin=0 when they could be stopped.

NASA's mission pages link for SpinSat says the following:

Operational Protocols

ESP thrusters are physically arranged on the exterior of the satellite to provide two basic maneuvers as spin-up (de-spin) maneuver and a normal thrust maneuver. For the spin-up maneuver, pairs of thrusters are co-aligned 180 degrees apart, and provide a tangential component force on the exterior; for de-spin, a 2nd pair of thrusters provide the opposite force. For the normal thrust maneuver, thrusters are oriented perpendicular to the exterior of the satellite to provide force in the normal direction. Another set of thrusters placed at the opposite pole provide normal force in the opposite direction. The space situational awareness component of the mission is a ground based observational plan to detect, characterize and assess state changes in the spacecraft. These observations are verified by data collected on the spacecraft by MEMS gyroscopes and accelerometers used to determine the spin axis orientation and spin rate of the spacecraft before during and after thruster firings. The spacecraft itself acts as the primary sensor for the third experiment, with a well-determined and characterized ballistic coefficient the routine collection of radar tracking and satellite laser ranging data will provide a high resolution atmospheric drag data set used to deriver thermospheric density.

How did it all go?

note: There are a few unique features of this kind of solid propellant thruster. You activate it using a low current, high voltage arc to simultaneously vaporize and ignite the propellant mixture. Shut off the arc, and the propellant becomes inert. That means these solid propellant thrusters are considered safe enough to spend at least a short time inside the crew area of the ISS.

I've asked separately about the principle with which electric solid thrusters actually operate.

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

enter image description here

$\endgroup$
  • 2
    $\begingroup$ "According to USSTRATCOM, the SpinSat satellite reentered Earth's atmosphere on March 11, 2017 at 23:47 UTC, falling into the Pacific Ocean southwest of Mexico " directory.eoportal.org/web/eoportal/satellite-missions/s/… $\endgroup$ – Organic Marble Sep 22 at 1:03
  • 1
    $\begingroup$ @OrganicMarble thanks for the link! That section is a really interesting read, made much easier when I realized it's written in reverse chronological order. It seems to be a very ambitious project. $\endgroup$ – uhoh Sep 22 at 1:38
  • 1
    $\begingroup$ Somehow this whole thing was off my radar completely, thanks for bringing it up again. $\endgroup$ – Organic Marble Sep 22 at 1:38
  • 1
    $\begingroup$ Very cool, but "millipound" sets my teeth on edge! $\endgroup$ – Camille Goudeseune Sep 22 at 2:48
3
$\begingroup$

When the results of the experiment become public, they should become visible on the NASA page you linked to. I haven't found anything in NTRS or on the website of the Naval Research Laboratory that runs the experiment.

Spinsat was launched from the ISS on Nov. 28, 2014.

This page has some details on what happened after launch:

• Sept. 2015: Already in early 2015, researchers at the AFRL (Air Force Research Laboratory) began their collaboration with the NRL SpinSat team, with the goal of using multiple AMOS (Advanced Maui Optical and Space Surveillance) sensors to observe the satellite firing the ESP micro-thruster thrusters, and turning the LEDs on and off. The observational goals include: 1) obtaining time-resolved, multi-band measurements of the satellite actively firing its micro-thrusters, 2) characterizing the detectability and spatial/temporal morphology of the ESP thruster plumes, 3) measuring the spin rate of the satellite with the LEDs turned on, ideally before and after a spin rate adjustment maneuver, and 4) measuring the spin rate of the satellite in its completely inactive mode, using only passive observations of reflected light and/or thermal emissions. 12)

...

Summary of AMOS Observations: Multiple sensors from the AMOS observatory's 3.6 m and 1.6 m telescopes were used to observe the three passes shown in Figure 14. Table 2 includes color-coded summaries of the status and quality for the collected data sets. The sensors include two acquisition sensors (LAAT and AATS) which are small, side-mounted, co-aligned telescopes imaging visible-band emissions using silicon-based CCD detectors, each with a relatively wide field-of-view (WFOV) subtending ~30 arcmin. The 3.6 m and 1.6 m telescopes also host one or more narrow field-of-view (NFOV) sensors, subtending ~30 arcsec or less. Three of these NFOV sensors (DI, ARDI, and Flash) also image in the visible and near-infrared spectral bands using Si-based CCDs. The 3.6 m LWIR sensor, however, acquires NFOV imagery in two thermal-infrared bands simultaneously. The analysis concentrates on the data gathered during the second AMOS pass, which had the best observing geometry and employed both near-IR and thermal-IR sensors from the largest-available AEOS (Advanced Electro-Optical System) 3.6 m telescope.

Observed Light-Curves: Figure 15 shows three light-curve plots acquired by the AEOS telescope's LAAT, ARDI and LWIR sensors during the second AMOS pass. The brightness units are instrumental magnitudes normalized for range variations, which provide a logarithmic measure of whole-object brightness, with the effects of object-to-observer range variations removed (but otherwise not radiometrically calibrated). The upper panel (blue) shows data from the LAAT sensor (a 0.6 m acquisition telescope coaligned with the main 3.6 m telescope), within the approximate 0.85-1.0 µm spectral range using an 850 nm long-pass spectral filter. The middle panel (red) shows data from the ARDI sensor, which is mounted on the 3.6m telescope itself, measuring emissions in the ~0.7-1.0 µm range using an I-band filter; this sensor provided the best signal-to-noise quality data among all of the light-curve data. The bottom panel (green) shows data from one of the two channels of the narrow-field LWIR sensor, also mounted on the 3.6 m telescope, measuring thermal emissions in its N2 filter band spanning the ~10-13 µm spectral range.

$\endgroup$
  • $\begingroup$ Oh, I see! I didn't realize this was so recent. I'm confused by dates here. I think SpinSat was brought to the ISS by CRS-4 in 2014. But when I just typed "SpinSat Norad ID" I got this link: http://www.n2yo.com/satellite/?s=40314, but that says SpinSat was launched in 1998. Of course that same site claims CRS-4 was launched in 2012 (not 2014) so now I'm quite confused! $\endgroup$ – uhoh Jul 2 '16 at 17:34
  • 1
    $\begingroup$ @uhoh the convention for satellites deployed from the ISS is to treat them as "pieces" of the original launch, in this case the mission that launched Zarya (1998-067A). $\endgroup$ – Chris Jul 2 '16 at 17:54
  • $\begingroup$ @Chris I see, thanks! I've asked a follow-up question. $\endgroup$ – uhoh Jul 3 '16 at 0:17
  • $\begingroup$ I didn't know about the LEDs - this is quite an interesiting experiment! If the tangential thrusters fail, I think it can still "spin" using the reaction wheel. are there any backup thrusters or is it 100% "digital" :) ? $\endgroup$ – uhoh Jul 3 '16 at 2:15
  • $\begingroup$ NASA's mission pages link for SpinSat (your first link) has been updated and redirects. I've edited the question to reflect the new link, you might want to update the first link here. I've also un-accepted because the page still doesn't post any results. It's possible there is news of results elsewhere. $\endgroup$ – uhoh Sep 22 at 0:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.