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Wilmington, North Carolina once had a thriving Black middle class and an elected interracial government. In 1898 white supremacists used violence to overthrow that government, kill Black residents and drive many others from the city.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
A highly elliptical orbit (HEO) or highly eccentric orbit is an orbit of one body about another with high eccentricity, usually referring to one around Earth. Examples of inclined HEO orbits include Molniya orbits, named after the Molniya Soviet communication satellites which used them, and Tundra orbits. Many US satellites also have used these orbits, satellites such as the Trumpet electronics intelligence satellites. The acronym HEO normally is expanded to Highly Eccentric Orbit by orbital analysts since all orbits around planets, etc are ellipses - the term "highly elliptical" is not very clear as to what is exaggerated. It would be more proper to call these orbits "elongated" than "highly elliptical". Highly eccentric orbits have two main uses - as transfer orbits and as good orbits for communication with or surveillance of the Polar regions. The transfer orbit was proposed by the German scientist Walter Hohmann in 1925, it connects two circular orbits, a lower one and a higher one, with an eccentric orbit. There are many HEO orbits where a launch vehicle initially injects a spacecraft into a LEO orbit and then an upper stage injects the payload, intended to go to geosynchronous orbit, into a HEO transfer orbit and then a final stage or engine circularizes the payload in the intended geosynchronous orbit. When chosen for communications or surveillance, these extremely elongated orbits also can provide long dwell times at a point in the sky during the approach to, and descent from, apogee. Bodies moving through the long apogee dwell appear to move slowly, and remain at high altitude over Polar latitude ground sites for long periods of time. This makes these elliptical orbits useful for communications satellites. The Northern Hemisphere has far more landmass, and it belongs to historically competitive countries, so most HEO satellites are in orbits which maximize time over the Northern Polar regions. Most of the Southern Hemisphere is covered by water and has been less interesting to these adversarial countries. Geostationary orbits cannot serve polar latitudes because their elevation above the horizon from these ground sites is too low. The latitude limit for a GEO sat is 81 degrees with a practical limit of just above 75 degrees. Many GEO comm sats have custom "foot prints" and focus their signals at their primary service areas, so above 60 degrees a larger ground antenna and clear line of sight is needed. Sirius Satellite Radio used inclined HEO orbits, specifically the Tundra orbits, to keep two satellites positioned above North America while another satellite quickly sweeps through the southern part of its 24-hour orbit. The longitude above which the satellites dwell at apogee in the small loop remains relatively constant as Earth rotates. The three separate orbits are spaced equally around the Earth, but share a common ground track.
A Molniya orbit (Russian: Молния, IPA: [ˈmoɫnʲɪjə] , "Lightning") is a type of satellite orbit designed to provide communications and remote sensing coverage over high latitudes. It is a highly elliptical orbit with an inclination of 63.4 degrees, an argument of perigee of 270 degrees, and an orbital period of about half a sidereal day. The name comes from the Molniya satellites, a series of Soviet/Russian civilian and military communications satellites that have used this type of orbit since the mid-1960s. A variation on the Molniya orbit is the Three Apogee orbit, whose period is a third of a sidereal day. The Molniya orbit has a long dwell time over the hemisphere of interest, while moving very quickly over the other. In practice, this places it over either Russia or Canada for most of its orbit, providing a high angle of view to communications and monitoring satellites covering these high-latitude areas. Geostationary orbits, which are necessarily inclined over the equator, can only view these regions from a low angle, hampering performance. In practice, a satellite in a Molniya orbit serves the same purpose for high latitudes as a geostationary satellite does for equatorial regions, except that multiple satellites are required for continuous coverage. Satellites placed in Molniya orbits have been used for television broadcasting, telecommunications, military communications, relaying, weather monitoring, early warning systems and classified surveillance purposes.
Very low Earth orbit (VLEO) is a range of geocentric orbits with lowest altitudes (at perigee) below 400 km (250 mi). It is of increasing commercial importance in a variety of scenarios and for multiple applications, in both private and government satellite operations. Applications include Earth observation (especially gravity and magnetic fields), telecommunications, and rural internet access among others. Spacecraft may be put into a highly elliptical orbit around Earth with a perigee as low as 80 to 90 km (50 to 56 mi), surviving for multiple orbits. Sub-orbital flight and near space is sometimes considered to be the case up until 160 km of altitude above Earth.
The Space-Based Infrared System (SBIRS) is a United States Space Force system intended to meet the United States' Department of Defense infrared space surveillance needs through the first two to three decades of the 21st century. The SBIRS program is designed to provide key capabilities in the areas of missile warning, missile defense, battlespace characterization and technical intelligence via satellites in geosynchronous Earth orbit (GEO), sensors hosted on satellites in highly elliptical orbit (HEO), and ground-based data processing and control. A total of twelve satellites carrying SBIRS or STSS payloads had been launched: SBIRS GEO-1 (USA-230, 2011), SBIRS GEO-2 (USA-241, 2013), SBIRS GEO-3 (USA-273, 2017), SBIRS GEO-4 (USA-282, 2018), SBIRS GEO-5 (USA-315, 2021), SBIRS GEO-6 (USA-336, 2022), SBIRS HEO-1 (USA-184, 2006), SBIRS HEO-2 (USA-200, 2008), SBIRS HEO-3 (USA-259, 2014), STSS-ATRR (USA-205, 2009), STSS Demo 1 (USA-208, 2009) and STSS Demo 2 (USA-209, 2009). The manufacturing contract for SBIRS GEO-5 and SBIRS GEO-6 was awarded in 2014. Funding for SBIRS GEO-7 and SBIRS GEO-8 was canceled in 2019.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Shirley Chisholm, elected in 1968.