 The sun-facing side of the MinXSS spacecraft. The two hinged solar panels are in their deployed state. The science instrument apertures can be seen near the top. The tape-measure antenna extends beyond the top of the photo. Image taken after final integration of the spacecraft. | |
| Mission type | Solar physics,Space weather,Near space research |
|---|---|
| Operator | CU/LASP |
| COSPAR ID | 1998-067HU |
| SATCATno. | 41474U |
| Website | lasp |
| Mission duration | Flight model 1: 6 months (planned), 11.66 months (actual) Flight model 2: 5 years (planned) 9 years (elasped) |
| Spacecraft properties | |
| Spacecraft type | 3UCubeSat |
| Manufacturer | CU/LASP |
| Launch mass | 3.5163 kg |
| Dry mass | 3.5163 kg |
| Power | Consumes: 8.0 W (science mode) 5.3 W (safe mode) 2.8 W (phoenix mode) Max generation: 19 W |
| Start of mission | |
| Launch date | December 6, 2015, 08:44:57 (2015-12-06UTC08:44:57Z) UTC |
| Rocket | Atlas V 401 |
| Launch site | Kennedy Space Center |
| Contractor | United Launch Alliance |
| Entered service | 2016 May 16 |
| End of mission | |
| Last contact | 2017-05-06 02:37:26 UTC |
| Decay date | 2017 May 6 |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Low Earth |
| Perigee altitude | 402 kilometers (250 mi) |
| Apogee altitude | 402 kilometers (250 mi) |
| Inclination | 51.65 degrees |
| Period | 92.69 minutes |
| Epoch | July 4, 2016[1] |
| Instruments | |
| ModifiedAmptek X123 silicon drift detector Sun Position Sensor (SPS), X-ray Photometer (XP) | |
TheMiniature X-ray Solar Spectrometer (MinXSS)CubeSat was the first launchedNational Aeronautics and Space AdministrationScience Mission Directorate CubeSat with a science mission.[2] It was designed, built, and operated primarily by students at theUniversity of Colorado Boulder with professional mentorship and involvement from professors, scientists, and engineers in the Aerospace Engineering Sciences department and theLaboratory for Atmospheric and Space Physics, as well asSouthwest Research Institute,NASAGoddard Space Flight Center, and theNational Center for Atmospheric Research'sHigh Altitude Observatory. The mission principal investigator is Dr. Thomas N. Woods and co-investigators are Dr. Amir Caspi, Dr. Phil Chamberlin, Dr. Andrew Jones, Rick Kohnert, Professor Xinlin Li, Professor Scott Palo, and Dr. Stanley Solomon. The student lead (project manager,systems engineer) was Dr. James Paul Mason, who has since become a Co-I for the second flight model of MinXSS.
MinXSS launched on 2015 December 6 to theInternational Space Station as part of theOrbital ATKCygnus CRS OA-4 cargo resupply mission.[3] The launch vehicle was aUnited Launch AllianceAtlas V rocket in the 401 configuration. CubeSat ridesharing was organized as part of NASAELaNa-IX. Deployment from the International Space Station was achieved with aNanoRacks CubeSat Deployer on 2016 May 16.[4] Spacecraft beacons were picked up soon after byamateur radio operators around the world.[5][6] Commissioning of the spacecraft was completed on 2016 June 14[7] and observations of solar flares captured nearly continuously since then.[8] The altitude rapidly decayed in the last week of the mission as atmospheric drag increased exponentially with altitude. The last contact from MinXSS came on 2017-05-06 at 02:37:26 UTC from a HAM operator in Australia. At that time, some temperatures on the spacecraft were already in excess of 100 °C. (One temperature of >300 °C indicated that the solar panel had disconnected, suggesting this contact was only moments before disintegration.)[9] Science data spanning the entire mission are publicly available.[10]
The MinXSS mission is to measure the solar softX-ray spectrum from about 0.5keV (25Å) to 30 keV (0.4Å) with ~0.15 keVFWHMspectral resolution. This part of the solarelectromagnetic spectrum is where the largest enhancement fromsolar flares is expected to occur.[11] It also has an important impact on Earthionospheric chemistry. Despite this, prior measurements have been either low-resolution broadband, or high-resolution but very narrow bandpass (see image below).[12][13] The relatively recent creation of miniaturizedsilicon drift detectors has enabled the MinXSS measurements. MinXSS data will provide a means of probing thesolar corona—especially inactive regions andsolar flares—and will be used as an input for models of the Earth's upper atmosphere, particularly the ionosphere,thermosphere, andmesosphere.
MinXSS is also the first flight of the Blue Canyon Technologies XACTattitude determination and control system (ADCS), one of the only commercially available 3-axis ADCSs for CubeSats. It is performing even better than its specification.[14] This demonstrates that a critical technology for spacecraft has been successfully miniaturized and commercialized.
The primary science instrument onboard MinXSS is a modified Amptek X123 silicon drift detector. The instrument was modified to make it compatible with a space environment.[13] Specifically, heat transfer pads were placed on the hottest components of the electronics boards to provide a conductive thermal path for heat transfer. In atmosphere, the electronics can cool convectively, but operation in vacuum requires cooling via conduction and hence an improved conductive path. Additionally, a small aperture made oftungsten was attached to the front of the detector to reduce the likelihood of photon saturation and limit the field of view to ±4º. Finally, an additionalberyllium filter was mounted in front of the detector to reduce the number ofphotoelectrons reaching the detector.
There are two secondary science instruments: the X-ray Photometer (XP) and the Sun Position Sensor (SPS). XP is a singlephotodiode with a beryllium filter in front of it of nearly identical thickness to the sum of the two beryllium filters in front of the X123. The purpose of XP is provide an on-orbit cross-calibration for the X123: the sum of the X123 spectrum should be approximately equal to the XP measurement. SPS is a fineSun sensor with 2.4arcsec precision that consists of a planar quad-diode observing visible light, whose purpose is to provide fine knowledge of the solar position with respect to the X123 and XP optical axes to correct for any off-axis signal attenuation.
All instruments were calibrated at theNational Institute of Standards and Technology'sSynchrotron Ultraviolet Radiation Facility (SURF III).[12][15]
Despite the loose requirements placed on CubeSats compared to larger spacecraft missions, MinXSS underwent the same rigorous tests that are considered standard in the aerospace industry. The X123 primary science instrument was fully flight-qualified on twosounding rocket flights.[12][16] In addition to subsystem-level and system-level testing at the bench (i.e. in air at room temperature), the system also underwentthermal vacuum chamber cycle testing, thermal balance testing, vibration testing, and end-to-end communications testing.[13] Mission simulations were performed during thermal vacuum cycling and at the bench using a solar array simulator that was autonomously power toggled with realistic orbital insolation and eclipse periods. This ensured that the spacecraft would be power-positive on orbit.
The spacecraft uses a measuring tape antenna and an AstroDev Li-1 radio. The spacecraft periodically beacons and its signal can be picked up with amateurham radio operator equipment. Below are the communications specifications:[17]
Beacons recorded by ham radio operators can be sent to the MinXSS team (inKISS format) to contribute to overall data capture.[17]
The first critical hurdle for any deployed spacecraft is to establish communications with the ground. This was achieved on the first pass over the MinXSS ground station inBoulder, Colorado.[18] As a science mission, success is determined by receipt of useful scientific measurements. MinXSS first light was presented at a press briefing and a contributed poster during theAmerican Astronomical Society's 47thSolar Physics Division Meeting in Boulder, Colorado.[19][20][21] Over 40GOES C-class and 7M-class solar flares occurred in the first weeks of the MinXSS mission, and those observations were downlinked to the ground for analysis. The results of those analyses will be the subjects of several upcoming peer-review papers. Additionally, MinXSS was the first flight of the Blue Canyon Technologies XACT 3-axis attitude determination and control system (ADCS). It continuously performed exceptionally, with 8arcsecond (1-sigma) pointing, where the specification was for 11 arcseconds.[14]
A second MinXSS spacecraft was built in parallel with the first. MinXSS-2 is identical to MinXSS-1 except for:
MinXSS-2 is planned to deploy from theSpaceflight Industries SSO-A SmallSat Express mission,[22] using aSpaceXFalcon 9.[23] Launch happened on 3 December 2018, and MinXSS2 was deployed to orbit. The MinXSS-2 orbit ispolar andSun-synchronous at 10:30amLTDN, at approximately 575 km altitude, providing an estimated 4-year mission life.
MinXSS-2 was selected for 2 years of funding by NASA under the 2016 Heliophysics Technology and Instrument Development for Science (H-TIDeS) program.[24] MinXSS-2 also adds science involvement from theNaval Research Laboratory, with Dr. Harry Warren added as a co-investigator.
MinXSS was chosen as the 2016AIAA Small Satellite Mission of the Year during the 30th Annual AIAA/USUSmall Satellite Conference inLogan, UT.[25][26]
The MinXSS project was structured after theColorado Student Space Weather ExperimentCubeSat, which established the graduate projects course led byJoseph R. Tanner in the Aerospace Engineering Sciences department at theUniversity of Colorado Boulder. Students in the department have the choice to either complete a Master's thesis or take two semesters of the graduate projects course. Typically, 10-20 students will be involved in each of the concurrent projects. CSSWE and MinXSS heavily leveraged professionals at theLaboratory for Atmospheric and Space Physics. As of 2018 March 8, 40 graduate, 5 undergraduate, and two high school students have worked on the project. Roughly 40 professionals have contributed with varying levels of involvement, from providing feedback at design reviews to writing flight software.
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