Glossary

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The following terms and acronyms are used in this Handbook.

ADC: Analog to digital 
ABMAG: –2.5 log (Fn) – 48.60 where Fn is the flux from the source in erg 
cm–2 sec-1 Hz-1 
ABn: Correction to ABMAG to account for the fact that the source spec-
trum is not constant in Fn (ABMAG=V+ABn) 
ACS: Advanced Camera for Surveys 
APT: Astronomer’s Proposal Tool 
aXe: Spectroscopic Data Extraction Software 
BOP: Bright Object Protection 
calacs: ACS calibration pipeline software 
CCD: Charge Coupled Device. Solid-state, light detecting device 
CMD: Color Magnitude Diagram 
CP: Call for Proposals 
CR: Cosmic ray 
CR-SPLIT: Division of a CCD exposure into shorter exposures to be used 
for cosmic ray rejection 
CTE: Charge transfer efficiency 
CVZ: Continuous viewing zone 
DN: Data number 
ETC: Exposure Time Calculator. ETCs are Web-based tools which can be 
accessed through the ACS Web pages. 
ERO: Early release observations 
FGS: Fine Guidance Sensors 
FOS: Faint Object Spectrograph 
FOV: Field of view 
FTP: File Transfer Protocol. Basic tool used to retrieve files from a remote 
system. Ask your system manager for information about using FTP. 
FUV: Far ultraviolet (~912 to 2000 Å) 
FWHM: Full width at half maximum 
GALEX: Galaxy Evolution Explorer 
GHRS: Goddard High-Resolution Spectrograph 
GO: General Observer 
GSC: Guide Star Catalog 
GSCII: Guide Star Catalog II 
GTO: Guaranteed Time Observer 
Help Desk: Facility for getting help on HST related topics via email. 
help@stsci.edu. 
HRC: High Resolution Channel 
HST: Hubble Space Telescope 
IDT: Investigation Definition Team 
IR: Infrared 
IRAF: Image Reduction and Analysis System. The environment in which 
STSDAS operates. 
ISR: Instrument Science Report 
IUE: International Ultraviolet Explorer Satellite 
K: Degree Kelvin 
L-flats: Low Frequency Variations Flats 
LMC: Large Magellanic Cloud 
MAMA: Multi-Anode Microchannel Array 
MCP: Microchannel Plate 
MPP: Multi Pinned Phased, a CCD mode that reduces dark current rate 
NICMOS: Near-Infrared Camera and Multi-Object Spectrograph 
NUV: Near ultraviolet (~2000 to 4000 Å) 
OTA: Optical Telescope Assembly 
PASP: Publications of the Astronomical Society of the Pacific 
PC: Program Coordinator 
Phase I proposal: A proposal for observing time on HST 
Phase II program: An approved HST program; includes precise detail of 
how program is to be executed 
PI: Principal investigator 
P-flats: pixel-to-pixel high-frequency flats 
PRF: Pixel Response Function 
PSF: Point-spread function. 
PyRAF: version of IRAF implemented in the Python language 
QE: Quantum Efficiency 
QEH: Quantum Efficiency Hysteresis 
Quadrant: Section of detector that is read-out by an amplifier. For WFC, 
there are 4 amplifiers, two for each detector, so each amplifier reads 
one 2048 x 2048 pixel quadrant. 
RA: Right Ascension 
RAS: HST simulator used in ground tests to accurately simulate the full 
field OTA illumination, and is used to calibrate HST instruments. 
Also know as RAS/HOMS, the Refractive Aberrated Simula-
tor/Hubble Opto-Mechanical Simulator. 
reference file: data file containing ACS parameters or calibration informa-
tion which is used by the calibration pipeline  
rms: Root mean square 
RQE: Responsive Quantum Efficiency 
SAA: South Atlantic anomaly 
SBC: Solar-Blind Channel 
SDSS: Sloan Digital Sky Survey 
SITe: Scientific Image Technologies; company that designed the ACS 
CCDs 
SLIM: Slitless Spectroscopy Simulator 
SMOV: Servicing Mission Observatory Verification 
S/N: signal-to-noise ratio 
SNAPSHOT: Short exposures taken during unused blocks of telescope 
time. 
ST-ECF: Space Telescope European Coordinating Facility 
STAN: Space Telescope Analysis Newsletter 
STIS: Space Telescope Imaging Spectrograph 
STScI: Space Telescope Science Institute 
STSDAS: Space Telescope Science Data Analysis System. The complete 
suite of IRAF data analysis and calibration routines used to process 
HST data. 
synphot: STSDAS synthetic photometry (IRAF) software package 
TAC: Telescope Allocation Committee 
TECs: Thermal Electric Coolers 
Tiny Tim: PSF simulation software developed by John Krist & 
Richard Hook 
URL: Uniform resource locator. Address for WWW. 
UV: Ultraviolet 
WFC: Wide-Field Channel 
WFPC2: Wide Field Planetary Camera-2. Replacement for WF/PC 
installed during first servicing mission of December 1993. 
WWW: World Wide Web. Hypertext-oriented method for finding and 
retrieving information over the Internet.