3 ANTENNA SITES

Table 1 gives the geographic locations of the ten stations comprising the VLBA, plus the 2-character codes used to identify them (Napier 1995). The stations are ordered East through West. All locations are based on the WGS84 ellipsoid used by the GPS system, with Earth radius $a=6378.137$ km and flattening $1/f=298.257223563$. See Napier (1995) for further site information.

Table 1: Geographic Locations of VLBA Stations

	North	West
	Latitude	Longitude	Elevation	Code
Location	[ $^{\circ}\ '\ ''$]	[ $^{\circ}\ '\ ''$]	[m]
Saint Croix, VI	17:45:23.68	64:35:01.07	16	SC
Hancock, NH	42:56:00.99	71:59:11.69	296	HN
North Liberty, IA	41:46:17.13	91:34:26.88	222	NL
Fort Davis, TX	30:38:06.11	103:56:41.34	1606	FD
Los Alamos, NM	35:46:30.45	106:14:44.15	1962	LA
Pie Town, NM	34:18:03.61	108:07:09.06	2365	PT
Kitt Peak, AZ	31:57:22.70	111:36:44.72	1902	KP
Owens Valley, CA	37:13:53.95	118:16:37.37	1196	OV
Brewster, WA	48:07:52.42	119:40:59.80	250	BR
Mauna Kea, HI	19:48:04.97	155:27:19.81	3763	MK

Several other radio telescopes often participate in VLBI observing in conjunction with the VLBA. A total of up to 100 hours per four-month trimester has been reserved for a High Sensitivity Array (HSA), composed currently of the VLBA, Green Bank Telescope (GBT: an NRAO facility), Arecibo (operated by the National Astronomy and Ionosphere Center), and Effelsberg (operated by the Max-Planck-Institut für Radioastronomie). The HSA is described at http://www.nrao.edu/HSA/ ; locations of the HSA telescopes are listed in Table 2. HSA observing proposals are addressed in Section 17.1.

The Very Large Array was a major adjunct participant in HSA and other VLBA observations until the original VLA correlator was shut down in January 2010. Earlier references to the VLA have been retained throughout this document in anticipation of a re-implemented phased-array capability in the Expanded Very Large Array (EVLA), which is expected toward the end of the current commisssioning process. Although no date has been established for resumption of VLBI co-observations by the EVLA, initial testing has yielded promising results.

The VLBA joins with the European VLBI Network (EVN) in a global cm-wave VLBI network during EVN sessions, and with networks of geodetic stations during global campaigns. Proposals for these and other, less frequent worldwide collaborative observations are described in Section 17.1.

Table 2: Locations of HSA Telescopes

	North	West
	Latitude	Longitude	Elevation	Code
Location	[ $^{\circ}\ '\ ''$]	[ $^{\circ}\ '\ ''$]	[m]
Arecibo, PR	18:20:36.60	66:45:11.10	497	AR
Green Bank, WV	38:25:59.24	79:50:23.41	807	GB
EVLA, NM	34:04:43.75	107:37:05.91	2115	Y27
Effelsberg, Germany	50:31:30	$-$6:53:00.3	319	EB