Results 51 to 60 of about 18,526 (302)

Very Low Earth Orbit Constellations for Earth Observation [PDF]

, 2022
Very Low Earth Orbits (VLEOs), those below 450 km, present a number of benefits and challenges for the development and operation of Earth observation spacecraft at both the system and mission level. This paper examines the design of constellations of satellites for operation in VLEO for Earth observation considering both system and mission level trade ...
Crisp, Nicholas H., Mcgrath, Ciara N., Roberts, Peter C. E., Edmondson, Steve, Haigh, Sarah J., Holmes, Brandon E. A., Macario Rojas, Alejandro, Oiko, Vitor T. A., Sinpetru, Luciana A., Smith, Katharine L., et al.   +10 more
openaire   +3 more sources

A Sensitivity Study of POD Using Dual-Frequency GPS for CubeSats Data Limitation and Resources

Remote Sensing, 2020
Making use of dual-frequency (DF) global navigation satellite system (GNSS) observations and good dynamic models, the precise orbit determination (POD) for the satellites on low earth orbits has been intensively investigated in the last decades and has ...
Kan Wang, Amir Allahvirdi-Zadeh, Ahmed El-Mowafy, Jason N. Gross   +3 more
doaj   +1 more source

An upstream open reading frame regulates expression of the mitochondrial protein Slm35 and mitophagy flux

FEBS Letters, EarlyView.
This study reveals how the mitochondrial protein Slm35 is regulated in Saccharomyces cerevisiae. The authors identify stress‐responsive DNA elements and two upstream open reading frames (uORFs) in the 5′ untranslated region of SLM35. One uORF restricts translation, and its mutation increases Slm35 protein levels and mitophagy.
Hernán Romo‐Casanueva, Ariann E. Mendoza‐Martínez, P. Abril Medina‐Flores, Carlos Campero‐Basaldua, Alexander DeLuna, Soledad Funes   +5 more
wiley   +1 more source

Solving Complex Low Earth Orbit-to-Geostationary Earth Orbit Transfer Problems Using Uniform Trigonometrization Method

Aerospace
Low-thrust orbit transfer problems are central to reducing mission costs and enabling cleaner, more efficient space travel. However, they remain difficult to solve using mathematically superior indirect methods of optimization.
Jackson T. Hurley, Kshitij Mall, Zhenbo Wang   +2 more
doaj   +1 more source

Low-Thrust Transfer Design of Low-Observable Geostationary Earth Orbit Satellite

International Journal of Aerospace Engineering, 2015
With radar and surface-to-air missiles posing an increasing threat to on-orbit spacecraft, low-observable satellites play an important role in low-thrust transfers.
Bing Hua, Zhujun Shao
doaj   +1 more source

LEO Enhanced Global Navigation Satellite System (LeGNSS): progress, opportunities, and challenges

Geo-spatial Information Science, 2021
With the completion of Chinese BeiDou Navigation Satellite System (BDS), the world has begun to enjoy the Positioning, Navigation, and Timing (PNT) services of four Global Navigation Satellite Systems (GNSS).
Haibo Ge, Bofeng Li, Song Jia, Liangwei Nie, Tianhao Wu, Zhe Yang, Jingzhe Shang, Yanning Zheng, Maorong Ge   +8 more
doaj   +1 more source

Fused Low-Earth-Orbit GNSS

IEEE Transactions on Aerospace and Electronic Systems
Traditional Global Navigation Satellite System (GNSS) immunity to interference may be approaching a practical performance ceiling. Greater gains are possible outside traditional GNSS orbits and spectrum. GNSS from low Earth orbit (LEO) has long been viewed as promising but expensive, requiring large constellations for rapid navigation solutions.
Peter A. Iannucci, Todd E. Humphreys
openaire   +2 more sources

In situ molecular organization and heterogeneity of the Legionella Dot/Icm T4SS

FEBS Letters, EarlyView.
We present a nearly complete in situ model of the Legionella Dot/Icm type IV secretion system, revealing its central secretion channel and identifying new components. Using cryo‐electron tomography with AI‐based modeling, our work highlights the structure, variability, and mechanism of this complex nanomachine, advancing understanding of bacterial ...
Przemysław Dutka, Yuxi Liu, Stefano Maggi, Debnath Ghosal, Jue Wang, Prashant P. Damke, Stephen D. Carter, Wei Zhao, Sukhithasri Vijayrajratnam, Joseph P. Vogel, Carrie L. Shaffer, Grant J. Jensen   +11 more
wiley   +1 more source

Sequence determinants of RNA G‐quadruplex unfolding by Arg‐rich regions

FEBS Letters, EarlyView.
We show that Arg‐rich peptides selectively unfold RNA G‐quadruplexes, but not RNA stem‐loops or DNA/RNA duplexes. This length‐dependent activity is inhibited by acidic residues and is conserved among SR and SR‐related proteins (SRSF1, SRSF3, SRSF9, U1‐70K, and U2AF1).
Naiduwadura Ivon Upekala De Silva, Puspa Kunwar, Md Ibnul Rifat Rahman, Joanna Koryo Kwao, Nathan Lehman, Zihan Zhang, Trenton Paul, Claire Cheng, Nicholas Truex, Hui‐Ting Lee, Jun Zhang   +10 more
wiley   +1 more source

Advancing Global Connectivity Through Low Earth Orbit Satellite Systems [PDF]

Iranian Journal of Information Processing & Management
Background: Satellite systems which orbit in Low Earth Orbit (LEO) are one of the innovative solutions to enable the connectivity in segregated geophysical parts of the world which are left out of the digital society, as they provide almost instantaneous,
Othman A. Hanshal, Suhad Qasim G. Haddad, Momunova Aigul Abdykerimovna, Hussain Kassim Ahmad, Faris Abdul Kareem Khazal   +4 more
doaj   +1 more source