|
Size: 9600
Comment:
|
Size: 13743
Comment:
|
| Deletions are marked like this. | Additions are marked like this. |
| Line 7: | Line 7: |
| This page summarizes the '''present instrumentation''' installed at the 30m observatory. [[BR]] The current system '''status''' is described [http://www.iram.es/IRAMES/mainWiki/TelescopeSystemStatus here]. | This page summarizes the '''present instrumentation''' installed at the 30m observatory. [[BR]] The current system '''status''' is described [http://www.iram.es/IRAMES/mainWiki/TelescopeSystemStatus on a second page]. |
| Line 14: | Line 14: |
| * Eight single pixel receivers A,B,C,D, and the 3x3 dual-polarisation HERA receiver are installed. | * Eight single pixel receivers A,B,C,D, and the 3x3 dual-polarisation HERA receiver are installed in the [http://www.iram.es/IRAMES/telescope/telescopeSummary/receiver6.html receiver cabin]. |
| Line 18: | Line 18: |
| * [http://www.iram.es/IRAMES/telescope/telescopeSummary/receiver3.html Plots of the receiver characteristics (taken 2000)] | * [http://www.iram.es/IRAMES/telescope/telescopeSummary/receiver3.html Plots of the receiver characteristics taken 2007] |
| Line 20: | Line 20: |
| ||'''Rx''' ||'''Pol'''|| || || || || ||'''tuning range''' || '''Trx''' || '''IF''' || '''IF Bw''' || '''Gim''' || '''Remarks''' || || || || || || || || ||'''[GHz]''' || '''[K]''' || '''[GHz]''' || '''[GHz]''' || '''[dB]''' || || ||A100 || V || X || || X || || ||(72-)80.0-115.5 || 60-80 || 1.5 || 0.5 || >20 || '''1. '''|| ||B100 || H || X || || || X || ||(72-)81.0-115.5 || 60-85 || 1.5 || 0.5 || >20 || '''1.'''|| ||C150 || V || || X || || X || ||130-183 || 70-125 || 4 || 1 || 15-25 || || ||D150 || H || || X || X || || ||130-183 || 80-125 || 4 || 1 || 08-17 || || ||A230 || V || X || || X || || ||197-266 || 85-150 || 4 || 1 || 12-17 || || ||B230 || H || X || || || X || ||197-266 || 95-160 || 4 || 1 || 12-17 || || ||C270 || V || || X || || X || ||241-281 || 125-250 || 4 || 1 || 10-20 || '''2.'''|| ||D270 || H || || X || X || || ||241-281 || 150-250 || 4 || 1 || 9-13 || '''2.'''|| ||HERA1 || H || || || || || X || 215-272 || 110-380 || 4 || 1 || ~10 || '''2.,3.'''|| ||HERA2 || V || || || || || X || 215-241 || 120-340 || 4 || 1 || ~10 || '''2.,3.'''|| |
||'''Rx''' ||#||'''Pol'''|||||||||| '''Rx combinations''' ||'''tuning range''' || '''Trx''' || '''IF''' || '''IF Bw''' || '''Gim''' || '''Rem.''' || || || || || '''AB''' || '''CD''' || '''AD''' || '''BC''' || ||'''[GHz]''' || '''[K]''' || '''[GHz]''' || '''[GHz]''' || '''[dB]''' || || ||A100 || 1|| V || X || || X || || ||(72-)80.0-115.5 || 60-80 || 1.5 || 0.5 || >20 || '''1. '''|| ||B100 || 1|| H || X || || || X || ||(72-)81.0-115.5 || 60-85 || 1.5 || 0.5 || >20 || '''1.'''|| ||C150 || 1|| V || || X || || X || ||130-183 || 70-125 || 4 || 1 || 15-25 || || ||D150 || 1|| H || || X || X || || ||130-183 || 80-125 || 4 || 1 || 08-17 || || ||A230 || 1|| V || X || || X || || ||197-266 || 85-150 || 4 || 1 || 12-17 || || ||B230 || 1|| H || X || || || X || ||197-266 || 95-160 || 4 || 1 || 12-17 || || ||C270 || 1|| V || || X || || X || ||241-281 || 125-250 || 4 || 1 || 10-20 || '''2.'''|| ||D270 || 1|| H || || X || X || || ||241-281 || 150-250 || 4 || 1 || 9-13 || '''2.'''|| ||HERA1 || 9|| H || || || || || X || 215-272 || 110-380 || 4 || 1 || ~10 || '''2.,3.'''|| ||HERA2 || 9|| V || || || || || X || 215-241 || 120-340 || 4 || 1 || ~10 || '''2.,3.'''|| * [http://www.iram.es/IRAMES/groups/receiver/receiver.html More information on the heterodyne receivers.] |
| Line 35: | Line 38: |
| 1. Using a special external LO, frequencies down to 77 GHz can be measured with good sideband rejection. For frequencies below 77 GHz, the sideband recection becomes weaker, and the sideband ratio reaches unity at 72 GHz | 1. Using a special external LO, frequencies down to 77 GHz can be measured with good sideband rejection. For frequencies below 77 GHz, the sideband recection becomes weaker, and the sideband ratio reaches unity at 72 GHz. [http://www.iram.fr/IRAMFR/PV/lowfreqs/report.ps.gz Test report of 2004], [http://www.iram.fr/IRAMFR/PV/lowfreqs/spectra.html Test spectra] |
| Line 39: | Line 42: |
| 1. [http://www.iram.es/IRAMES/mainWiki/HeraWebPage More information on HERA ] | 1. HERA is a heterodyne receiver array consisting of two arrays of 3x3 pixels with 24" spacing. The two arrays have orthogonal polarization (V, H) the two polarizations pointing at identical locations on the sky. HERA is equipped with a derotator allowing to follow a source in the sky maintaining the same "footprint". The tunable range is between 215 and 272 GHz. In this range the beamwidth varies between 12" and 9". * [http://www.iram.es/IRAMES/otherDocuments/manuals/HERA_manual_v20.pdf HERA manual, version 2.0] by Schuster et al. 2006 * [http://esoads.eso.org/abs/2004A%26A...423.1171S Schuster et al. 2004, A&A, 423, 1171] A 230 GHz Heterodyne Receiver Array for the IRAM 30m telescope ([http://www.iram.es/IRAMES/otherDocuments/manuals/0179hera.pdf local copy]) |
| Line 44: | Line 52: |
| Two large field bolometer cameras are installed: '''MAMBO1''' with 37 pixels, and '''MAMBO2''' with 117 pixels. Usually MAMBO2 is in use. Both cameras work at 1.2mm wavelength, the HPBW is 11 arcsec, pixel spacing is 20 arcsec, and the sensitivity is 1.5mJy. This is the rms after 10 minutes integration (normal bolometric conditions) with skynoise removal. See [http://www.iram.es/IRAMES/mainWiki/MamboWebPage the MAMBO page for details.] | Two large field bolometer cameras are installed: '''MAMBO1''' with 37 pixels, and '''MAMBO2''' with 117 pixels ([http://www.mpifr-bonn.mpg.de/div/bolometer/#mamgo MAx-Planck Millimeter BOlometer Array]). Usually MAMBO2 is in use. Both cameras work at 1.2mm wavelength, the HPBW is 11", pixel spacing is 20", and the sensitivity is 1.5mJy. This is the rms after 10 minutes integration (normal bolometric conditions) with skynoise removal. See [http://www.iram.es/IRAMES/mainWiki/MamboWebPage the MAMBO page for details.] |
| Line 48: | Line 56: |
| == Efficiencies and Half-power beam width == | == Telescope efficiencies and beam widths == |
| Line 50: | Line 58: |
| * Below you find the most recent values for the forward and beam efficiencies. We have also compiled the [http://www.iram.es/IRAMES/telescope/telescopeSummary/effi_history.html value of the efficiencies in the past]. | * Below you find the forward and beam efficiencies measured in March 2005 ([http://www.iram.fr/IRAMFR/ARN/aug05/node6.html IRAM Newsletter 8/05]). |
| Line 52: | Line 60: |
| * Here you can find the [http://www.iram.es/IRAMES/telescope/telescopeSummary/beam_effis.html plot of efficiencies measured in 2000]. A more recent compilation can be found in the Annual Report 2007. | || '''freq''' || '''HPBW''' || '''Beff''' || '''S/TA*''' || '''Feff''' || || '''(GHz)''' || '''(arcsec)''' || '''(%)''' || '''(Jy/K)''' || '''(%)''' || || || (1) || (2) || (3) || (4) || ||72 (extrapolated) || 34 || 79 || 6.0 || 95 || ||77 (extrapolated) || 32 || 79 || 6.0 || 95 || ||86 ||29 || 78 || 6.0 || 95 || ||110 || 22 || 75 || 6.3 || 95 || ||145 || 17 || 69 || 6.7 || 93 || ||170 || 14.5 || 65 || 7.1 || 93 || ||210 || 12 || 57 || 7.9 || 91 || ||235 || 10.5 || 52 || 8.7 || 91 || ||260 || 9.5 || 46 || 9.5 || 88 || ||279 || 9 || 42 || 10.4 || 88 || |
| Line 54: | Line 74: |
| || freq || HPBW || Beff || S/TA* || Feff || || (GHz) || (arcsec) || (%) || (Jy/K) || (%) || || || (1) || (2) || (3) || (4) || ||72 (extrapolated) || 34 || 79 || 6.0 || 95 || ||77 (extrapolated) || 32 || 79 || 6.0 || 95 || ||86 ||29 || 78 || 6.0 || 95 || ||110 || 22 || 75 || 6.3 || 95 || ||145 || 17 || 69 || 6.7 || 93 || ||170 || 14.5 || 65 || 7.1 || 93 || ||210 || 12 || 57 || 7.9 || 91 || ||235 || 10.5 || 52 || 8.7 || 91 || ||260 || 9.5 || 46 || 9.5 || 88 || ||279 || 9 || 42 || 10.4 || 88 || |
1. The '''half power beam width, HPBW''', can be well fitted by: HPBW/arcsec = 2460/freq/GHz. |
| Line 68: | Line 76: |
| 1. The half power beam width, HPBW, can be well fitted by: HPBW/arcsec = 2460/freq/GHz. | 1. '''Main beam efficiency Beff'''. The data can be well fit by a Ruze function Beff = 1.2 epsilon exp[-(4pi R sigma/ lambda)^2] with sigma being the rms value of the telescope optics deformations, R the reduction factor for a steep main reflector, epsilon the aperture efficieny of the perfect telescope and lambda the wavelength in mm. The data can be fit by R*sigma = 0.07 and epsilon = 0.69. The aperture efficiency of the 30-m telescope can be obtained using eta_a=B_eff*0.79 |
| Line 70: | Line 78: |
| 1. Main beam efficiency Beff. The data can be well fit by a Ruze function Beff = 1.2 epsilon exp[-(4pi R sigma/ lambda)^2] with sigma being the rms value of the telescope optics deformations, R the reduction factor for a steep main reflector, epsilon the aperture efficieny of the perfect telescope and lambda the wavelength in mm. The data can be fit by R*sigma = 0.07 and epsilon = 0.69. The aperture efficiency of the 30-m telescope can be obtained using eta_a=B_eff*0.79 | 1. '''Point source sensitivity S/T_A*.''' For a Gaussian source and beam size, and a source which is much smaller than the beam, S(Jy)/T_mb(K)=8.18E-7*theta(")**2*nu(GHz)**2 (Rohlfs & Wilson, Tools of Radioastronomy (2. ed., Eq. 8.20). Using the approximation in 1) yields for the 30-m telescope S/T_mb=4.95 Jy/K. S/T_A* is obtained by multiplying 4.95 J/K with F_eff/B_eff. |
| Line 72: | Line 80: |
| 1. Point source sensitivity S/T_A*. For a Gaussian source and beam size, and a source which is much smaller than the beam, S(Jy)/T_mb(K)=8.18E-7*theta(")**2*nu(GHz)**2 (Rohlfs & Wilson, Tools of Radioastronomy (2. ed., Eq. 8.20). Using the approximation in 1) yields for the 30-m telescope S/T_mb=4.95 Jy/K. S/T_A* is obtained by multiplying 4.95 J/K with F_eff/B_eff. | 1. '''Forward efficiency Feff''': The values for Feff are valid after the 12th of December 2000 when a new reflecting ring was put around the secondary mirror. |
| Line 74: | Line 82: |
| 1. The values for F_eff are valid after the 12th of December 2000 when a new reflecting ring was put around the secondary mirror. The moon efficiencies are equal to forward efficiencies (Kramer et al. 1997). | * Historic values: [http://www.iram.es/IRAMES/telescope/telescopeSummary/beam_effis.html Plot of efficiencies against frequency, measured in 2000], [http://www.iram.es/IRAMES/telescope/telescopeSummary/effi_history.html Compilation of efficiencies obtained in the past till 2001]. |
| Line 79: | Line 88: |
| === Spectrometers === || || Type || Resolution || Bandwidth || Receiver (width mode) || Remark || |
|| || Type || Channel Width || Bandwidth || Receiver (width mode) || Remark || |
| Line 84: | Line 91: |
| || '''WILMA''' || Autocorrelator || 2 MHz || 18x930 MHz || HERA (wide) || || '''VESPA''' || Autocorrelator || 3.3 kHz-1.25 MHz || 10-512 MHz || all SIS receives incl. HERA (narrow) || (3) || || '''XPOL''' || VESPA || 40kHz-1.25MHz || 120-640MHz || A100 and B100 (narrow) || (4) || |
|| '''WILMA''' || Autocorrelator || 2 MHz || 18x930 MHz || HERA (wide) || (3) || || '''VESPA''' || Autocorrelator || 3.3 kHz-1.25 MHz || 10-512 MHz || all SIS receives incl. HERA (narrow) || (4) || || '''XPOL''' || VESPA || 40kHz-1.25MHz || 120-640MHz || A100 and B100 (narrow) || (5) || || '''ABBA''' || || || || || (6) || |
| Line 88: | Line 96: |
| 1. max 4 parts; series parallel or mixed mode possible; using the filterbanks with 1GHz bandwidth excludes the use of the AC or the 100 MHz FB with the same rx. The FB can be shifted in multiples of 32 MHz from the center frequency of the connected rx. | In general, several backends can be attached to one receiver. Exceptions are listed below. The [http://www.iram.es/IRAMES/documents/ncs30mPako/Current/PDF/pako.pdf pako manual] describes in detail how to configure the backends. |
| Line 90: | Line 98: |
| 1. max 9 parts; use of the 4 MHz FBs excludes the use of the AC or the 100kHz FB on the same receiver. Frequency switching not available. While the channel spacing is 4MHz, the 3dB width is 5.4 MHz and the noise equivalent width is 6.5 MHz | 1. '''1MHz Filterbank''': max. 4 parts; series, parallel, or mixed mode possible; using the 1MHz filterbank with 1GHz bandwidth excludes the use of VESPA with the same receiver. The filterbank can be shifted in multiples of 32MHz from the center frequency of the connected receiver. |
| Line 92: | Line 100: |
| 1. Up to 18000 channels. In connection with HERA (9 pixels) the following combinations of resolution (kHz) and bandwidth (MHz) are possible: (20/40), (40,80), (80, 160), (320,320), (1250, 640); [http://www.iram.es/IRAMES/otherDocuments/manuals/vespa_ug.ps VESPA User Guide (2002)], local contact: G. Paubert | 1. '''4MHz Filterbank''': max. 9 parts; use of the 4MHz filterbank excludes the use of VESPA on the same receiver. Frequency switching not available. While the channel spacing is 4MHz, the 3dB width is 5.4MHz and the noise equivalent width is 6.5 MHz |
| Line 94: | Line 102: |
| 1. Line and continuum polarimetry is possible at the 30m using a new type of IF polarimeter designated XPOL. The central feature of XPOL is the correlator VESPA where the IF signals from two orthogonally polarized receivers are cross correlated to determine the four Stokes parameters. A manual is in preparation, contact: C. Thum | 1. '''WILMA''': [http://www.iram.fr/IRAMFR/TA/backend/veleta/wilma/index.htm The Wideband Line Multiple Autocorrelator] for HERA |
| Line 96: | Line 104: |
| 1. '''VESPA''': [http://www.iram.fr/IRAMFR/TA/backend/veleta/vespa/index.htm The Versatile SPectrometer Array]. Up to 18000 channels. In connection with HERA (9 pixels) the following combinations of resolution (kHz) and bandwidth (MHz) are possible: (20/40), (40,80), (80, 160), (320,320), (1250, 640); [http://www.iram.es/IRAMES/otherDocuments/manuals/vespa_ug.ps VESPA User Guide (2002)], [http://www.iram.es/IRAMFR/ARN/dec02/node6.html Summary in IRAM Newsletter No. 54 (Dec 2002)], local contact: G. Paubert | |
| Line 97: | Line 106: |
| 1. '''XPOL''': Line and continuum polarimetry is possible at the 30m using a new type of IF polarimeter designated XPOL. The central feature of XPOL is the correlator VESPA where the IF signals from two orthogonally polarized receivers are cross correlated to determine the four Stokes parameters. A manual is in preparation, contact: C. Thum | |
| Line 98: | Line 108: |
=== Bolometer backends === * ABBA1 * ABBA2 |
1. '''ABBA1 and ABBA2''' (Adc Bolometer Backend) are the bolometer backends, i.e. dedicated PCs connected to the bolometers. |
| Line 123: | Line 126: |
| == Observing Modes == | == Observing Modes and Switching Modes == |
| Line 125: | Line 128: |
| || Observing mode || total power || chopping || position switching || beam switching || frequency switching || || '''Calibrate''' (Heterodyne) || X || || || || || || '''Pointing''' || || X || || || || || '''Focus''' || || X || || || || || '''Tip''' (Skydip) || || X || || || || || '''Track''' || X || || || || X || || '''ON-OFF''' || || || X || X || || || '''OTF''' (Heterodyne) || || || X || || X || || '''OTF''' (Bolometer) || || || || X || || || '''VLBI''' || || || || || || |
|| Observing mode || swTotal || swBeam || swWobbler || swFrequency || || '''Calibrate''' (Heterodyne) || X || || || || || '''Pointing''' || X || X || X || || || '''Focus''' || X || X || X || || || '''Tip''' (Skydip) || X || || || || || '''Track''' || || || || fsw || || '''ONOFF''' || psw || || wsw || || || '''OTFMAP''' (Heterodyne) || otf/psw || || || otf/fsw || || '''Raster''' || || || || || || '''OTFMAP''' (MAMBO Bolometer) || || || X || || || '''VLBI''' || X || || || || |
| Line 136: | Line 140: |
| * '''Pointing''': Using nearby (within 10 degree) pointing sources, <1" accuracy can be obtained; with absolute ("blind") pointing, the accuracy is <4", the receivers are usually aligned within 2" (see the [http://www.iram.es/IRAMES/mainWiki/TelescopeSystemStatus Telescope Status page] for current values). Checking the pointing and alignment (using e.g. a planet) is the responsibility of the observer. * '''Focus''': residual errors of <1mm may need correction. There may be systematic differences (<0.4") in the focus of the different receivers. Check focus at least at after sunrise and sunset. * '''Position switching''': only relative OFF positions possible (radio projection offsets). * '''Beam switching''' with wobbling secondary: max. 240" throw at 0.25 Hz, standard phase duration 0.5 Hz. * '''Frequency switching''': max. 45 km/s throw at max. 0.5 Hz., with 100 kHz filters and autocorrelator only * '''On the fly mapping (Heterodyne)''': Works with all receiver and backends, typical dump rate 0.5-1 Hz |
* for more details on observing and switching modes, see the section "NCS explained" in the [http://www.iram.es/IRAMES/documents/ncs30mPako/Current/PDF/pako.pdf pako cookbook] * '''swTotal''' stands for total power observations without switching, while still using the internal synchronization signals. * '''swBeam''' beam switched observations using the chopper wheel on mirror M4. * '''swWobbler''' switching the wobbling secondary (M2). The maximum allowed throw is +/-2'. * '''swFrequency''' switching the local oscillator frequency * '''Pointing''': Using nearby (within 10 degree) pointing sources, <1" accuracy can be obtained; with absolute ("blind") pointing, the accuracy is about 2" rms, the receivers are aligned within 1.7" (see the [http://www.iram.es/IRAMES/mainWiki/TelescopeSystemStatus Telescope Status page] for current values). Checking the pointing and alignment (using e.g. a planet) is the responsibility of the observer. * '''Focus''': residual errors of <1mm may need correction. There are systematic differences of upto 0.6mm in the focus of the different receivers (cf. [http://www.iram.es/IRAMES/mainWiki/TelescopeSystemStatus Telescope Status page]). The focus is subject to change especially during sunrise and sunset. * '''Position switching (psw)''': the combination of ONOFF with swTotal is called "Position Switching". Only relative off-source reference positions are possible. * '''Wobbler switching (wsw)''': often called '''double beam switching mode''': max. 240" throw at 0.25 Hz, standard phase duration 0.5 Hz. * '''Frequency switching (fsw)''': max. 45 km/s throw up to about 10 Hz. * '''On the fly mapping (Heterodyne)''': Works with all receivers and backends, typical dump rate 0.5 to 10 Hz. ''OTF can be observed without reference position, e.g. for galaxies, and MIRA is able to use emission-free OTF data as reference!'' * '''Raster mapping''' is at present '''not offered'''. The observer may want to use eigher psw or otf instead. |
| Line 144: | Line 157: |
| [#beginOfPage Back to top] | |
| Line 145: | Line 159: |
| == Weather station and Taumeter == * [http://mrt-lx3.iram.es/tau/meteo-main.php Weather station] *Wind velocity and direction measured on hill behind the telescope * Outside temperature and relative humidity measured at base of telescope * Pressure measured at entrance to control building * [http://mrt-lx3.iram.es/tau/taumeter-main-db.php Taumeter] does regular skydips to inform the observer about the sky transmission near '''225 GHz'''. The local oscillator works at 225GHz. The IF is 1.5GHz and the bandwidth is 0.5GHz. It is a double-sideband Schottky receiver. |
|
| Line 148: | Line 170: |
| Old [http://www.iram.es/IRAMES/telescope/telescopeSummary/telescope_summary.html Telescope System Summary page] | Old [http://www.iram.es/IRAMES/telescope/telescopeSummary/telescope_summary.html Telescope System Summary page of September 07] |
| Line 150: | Line 172: |
| Moderator: Carsten Kramer | This is page http://www.iram.es/IRAMES/mainWiki/TelescopeSystemSummary moderated by Carsten Kramer |
This page summarizes the present instrumentation installed at the 30m observatory. BR The current system status is described [http://www.iram.es/IRAMES/mainWiki/TelescopeSystemStatus on a second page].
Frontends
Heterodyne Receivers
Eight single pixel receivers A,B,C,D, and the 3x3 dual-polarisation HERA receiver are installed in the [http://www.iram.es/IRAMES/telescope/telescopeSummary/receiver6.html receiver cabin].
- Four of the 8 A,B,C,D receivers can be used simultaneously. HERA cannot be combined with other receivers.
[http://www.iram.es/IRAMES/telescope/telescopeSummary/receiver3.html Plots of the receiver characteristics taken 2007]
Rx |
# |
Pol |
Rx combinations |
tuning range |
Trx |
IF |
IF Bw |
Gim |
Rem. |
||||
|
|
|
AB |
CD |
AD |
BC |
|
[GHz] |
[K] |
[GHz] |
[GHz] |
[dB] |
|
A100 |
1 |
V |
X |
|
X |
|
|
(72-)80.0-115.5 |
60-80 |
1.5 |
0.5 |
>20 |
1. |
B100 |
1 |
H |
X |
|
|
X |
|
(72-)81.0-115.5 |
60-85 |
1.5 |
0.5 |
>20 |
1. |
C150 |
1 |
V |
|
X |
|
X |
|
130-183 |
70-125 |
4 |
1 |
15-25 |
|
D150 |
1 |
H |
|
X |
X |
|
|
130-183 |
80-125 |
4 |
1 |
08-17 |
|
A230 |
1 |
V |
X |
|
X |
|
|
197-266 |
85-150 |
4 |
1 |
12-17 |
|
B230 |
1 |
H |
X |
|
|
X |
|
197-266 |
95-160 |
4 |
1 |
12-17 |
|
C270 |
1 |
V |
|
X |
|
X |
|
241-281 |
125-250 |
4 |
1 |
10-20 |
2. |
D270 |
1 |
H |
|
X |
X |
|
|
241-281 |
150-250 |
4 |
1 |
9-13 |
2. |
HERA1 |
9 |
H |
|
|
|
|
X |
215-272 |
110-380 |
4 |
1 |
~10 |
2.,3. |
HERA2 |
9 |
V |
|
|
|
|
X |
215-241 |
120-340 |
4 |
1 |
~10 |
2.,3. |
[http://www.iram.es/IRAMES/groups/receiver/receiver.html More information on the heterodyne receivers.]
Remarks:
Using a special external LO, frequencies down to 77 GHz can be measured with good sideband rejection. For frequencies below 77 GHz, the sideband recection becomes weaker, and the sideband ratio reaches unity at 72 GHz. [http://www.iram.fr/IRAMFR/PV/lowfreqs/report.ps.gz Test report of 2004], [http://www.iram.fr/IRAMFR/PV/lowfreqs/spectra.html Test spectra]
- Noise increasing with frequency
- HERA is a heterodyne receiver array consisting of two arrays of 3x3 pixels with 24" spacing. The two arrays have orthogonal polarization (V, H) the two polarizations pointing at identical locations on the sky. HERA is equipped with a derotator allowing to follow a source in the sky maintaining the same "footprint". The tunable range is between 215 and 272 GHz. In this range the beamwidth varies between 12" and 9".
[http://www.iram.es/IRAMES/otherDocuments/manuals/HERA_manual_v20.pdf HERA manual, version 2.0] by Schuster et al. 2006
[http://esoads.eso.org/abs/2004A%26A...423.1171S Schuster et al. 2004, A&A, 423, 1171] A 230 GHz Heterodyne Receiver Array for the IRAM 30m telescope ([http://www.iram.es/IRAMES/otherDocuments/manuals/0179hera.pdf local copy])
[#beginOfPage Back to top]
Bolometers
Two large field bolometer cameras are installed: MAMBO1 with 37 pixels, and MAMBO2 with 117 pixels ([http://www.mpifr-bonn.mpg.de/div/bolometer/#mamgo MAx-Planck Millimeter BOlometer Array]). Usually MAMBO2 is in use. Both cameras work at 1.2mm wavelength, the HPBW is 11", pixel spacing is 20", and the sensitivity is 1.5mJy. This is the rms after 10 minutes integration (normal bolometric conditions) with skynoise removal. See [http://www.iram.es/IRAMES/mainWiki/MamboWebPage the MAMBO page for details.]
[#beginOfPage Back to top]
Telescope efficiencies and beam widths
Below you find the forward and beam efficiencies measured in March 2005 ([http://www.iram.fr/IRAMFR/ARN/aug05/node6.html IRAM Newsletter 8/05]).
freq
HPBW
Beff
S/TA*
Feff
(GHz)
(arcsec)
(%)
(Jy/K)
(%)
(1)
(2)
(3)
(4)
72 (extrapolated)
34
79
6.0
95
77 (extrapolated)
32
79
6.0
95
86
29
78
6.0
95
110
22
75
6.3
95
145
17
69
6.7
93
170
14.5
65
7.1
93
210
12
57
7.9
91
235
10.5
52
8.7
91
260
9.5
46
9.5
88
279
9
42
10.4
88
The half power beam width, HPBW, can be well fitted by: HPBW/arcsec = 2460/freq/GHz.
Main beam efficiency Beff. The data can be well fit by a Ruze function Beff = 1.2 epsilon exp[-(4pi R sigma/ lambda)^2] with sigma being the rms value of the telescope optics deformations, R the reduction factor for a steep main reflector, epsilon the aperture efficieny of the perfect telescope and lambda the wavelength in mm. The data can be fit by R*sigma = 0.07 and epsilon = 0.69. The aperture efficiency of the 30-m telescope can be obtained using eta_a=B_eff*0.79
Point source sensitivity S/T_A*. For a Gaussian source and beam size, and a source which is much smaller than the beam, S(Jy)/T_mb(K)=8.18E-7*theta(")**2*nu(GHz)**2 (Rohlfs & Wilson, Tools of Radioastronomy (2. ed., Eq. 8.20). Using the approximation in 1) yields for the 30-m telescope S/T_mb=4.95 Jy/K. S/T_A* is obtained by multiplying 4.95 J/K with F_eff/B_eff.
Forward efficiency Feff: The values for Feff are valid after the 12th of December 2000 when a new reflecting ring was put around the secondary mirror.
Historic values: [http://www.iram.es/IRAMES/telescope/telescopeSummary/beam_effis.html Plot of efficiencies against frequency, measured in 2000], [http://www.iram.es/IRAMES/telescope/telescopeSummary/effi_history.html Compilation of efficiencies obtained in the past till 2001].
[#beginOfPage Back to top]
Backends
|
Type |
Channel Width |
Bandwidth |
Receiver (width mode) |
Remark |
1 MHz |
Filterbank |
1 MHz |
4x256 MHz, 2x512 MHz, or, 1x1GHz |
A100, B100 (narrow), A230, B230, C150, D150, C270, D270 (narrow or wide) |
(1) |
4 MHz |
Filterbanks |
4 MHz |
9x1GHz |
either HERA1 or HERA2 (wide), all other SIS receivers (wide) except 3mm |
(2) |
WILMA |
Autocorrelator |
2 MHz |
18x930 MHz |
HERA (wide) |
(3) |
VESPA |
Autocorrelator |
3.3 kHz-1.25 MHz |
10-512 MHz |
all SIS receives incl. HERA (narrow) |
(4) |
XPOL |
VESPA |
40kHz-1.25MHz |
120-640MHz |
A100 and B100 (narrow) |
(5) |
ABBA |
|
|
|
|
(6) |
In general, several backends can be attached to one receiver. Exceptions are listed below. The [http://www.iram.es/IRAMES/documents/ncs30mPako/Current/PDF/pako.pdf pako manual] describes in detail how to configure the backends.
1MHz Filterbank: max. 4 parts; series, parallel, or mixed mode possible; using the 1MHz filterbank with 1GHz bandwidth excludes the use of VESPA with the same receiver. The filterbank can be shifted in multiples of 32MHz from the center frequency of the connected receiver.
4MHz Filterbank: max. 9 parts; use of the 4MHz filterbank excludes the use of VESPA on the same receiver. Frequency switching not available. While the channel spacing is 4MHz, the 3dB width is 5.4MHz and the noise equivalent width is 6.5 MHz
WILMA: [http://www.iram.fr/IRAMFR/TA/backend/veleta/wilma/index.htm The Wideband Line Multiple Autocorrelator] for HERA
VESPA: [http://www.iram.fr/IRAMFR/TA/backend/veleta/vespa/index.htm The Versatile SPectrometer Array]. Up to 18000 channels. In connection with HERA (9 pixels) the following combinations of resolution (kHz) and bandwidth (MHz) are possible: (20/40), (40,80), (80, 160), (320,320), (1250, 640); [http://www.iram.es/IRAMES/otherDocuments/manuals/vespa_ug.ps VESPA User Guide (2002)], [http://www.iram.es/IRAMFR/ARN/dec02/node6.html Summary in IRAM Newsletter No. 54 (Dec 2002)], local contact: G. Paubert
XPOL: Line and continuum polarimetry is possible at the 30m using a new type of IF polarimeter designated XPOL. The central feature of XPOL is the correlator VESPA where the IF signals from two orthogonally polarized receivers are cross correlated to determine the four Stokes parameters. A manual is in preparation, contact: C. Thum
ABBA1 and ABBA2 (Adc Bolometer Backend) are the bolometer backends, i.e. dedicated PCs connected to the bolometers.
[#beginOfPage Back to top]
Control System
The 30-m telescope runs under the New Control System (NCS), see:
[http://www.iram.es/IRAMES/ncs30m/ NCS documentation] [http://mrt-lx1/mainWiki/ Wiki with up-to-date Notes on NCS]
Observing modes and source offsets in:
- Projection "Radio" (same offsets as in old CS) in Equatorial J2000.0
- "true angle" horizontal
- Nasmyth (receiver offsets)
[#beginOfPage Back to top]
Observing Modes and Switching Modes
Observing mode |
swTotal |
swBeam |
swWobbler |
swFrequency |
Calibrate (Heterodyne) |
X |
|
|
|
Pointing |
X |
X |
X |
|
Focus |
X |
X |
X |
|
Tip (Skydip) |
X |
|
|
|
Track |
|
|
|
fsw |
ONOFF |
psw |
|
wsw |
|
OTFMAP (Heterodyne) |
otf/psw |
|
|
otf/fsw |
Raster |
|
|
|
|
OTFMAP (MAMBO Bolometer) |
|
|
X |
|
VLBI |
X |
|
|
|
for more details on observing and switching modes, see the section "NCS explained" in the [http://www.iram.es/IRAMES/documents/ncs30mPako/Current/PDF/pako.pdf pako cookbook]
swTotal stands for total power observations without switching, while still using the internal synchronization signals.
swBeam beam switched observations using the chopper wheel on mirror M4.
swWobbler switching the wobbling secondary (M2). The maximum allowed throw is +/-2'.
swFrequency switching the local oscillator frequency
Pointing: Using nearby (within 10 degree) pointing sources, <1" accuracy can be obtained; with absolute ("blind") pointing, the accuracy is about 2" rms, the receivers are aligned within 1.7" (see the [http://www.iram.es/IRAMES/mainWiki/TelescopeSystemStatus Telescope Status page] for current values). Checking the pointing and alignment (using e.g. a planet) is the responsibility of the observer.
Focus: residual errors of <1mm may need correction. There are systematic differences of upto 0.6mm in the focus of the different receivers (cf. [http://www.iram.es/IRAMES/mainWiki/TelescopeSystemStatus Telescope Status page]). The focus is subject to change especially during sunrise and sunset.
Position switching (psw): the combination of ONOFF with swTotal is called "Position Switching". Only relative off-source reference positions are possible.
Wobbler switching (wsw): often called double beam switching mode: max. 240" throw at 0.25 Hz, standard phase duration 0.5 Hz.
Frequency switching (fsw): max. 45 km/s throw up to about 10 Hz.
On the fly mapping (Heterodyne): Works with all receivers and backends, typical dump rate 0.5 to 10 Hz. OTF can be observed without reference position, e.g. for galaxies, and MIRA is able to use emission-free OTF data as reference!
Raster mapping is at present not offered. The observer may want to use eigher psw or otf instead.
Polarimetry: using VESPA as an IF polarimeter
[#beginOfPage Back to top]
Weather station and Taumeter
[http://mrt-lx3.iram.es/tau/meteo-main.php Weather station]
- Wind velocity and direction measured on hill behind the telescope
- Outside temperature and relative humidity measured at base of telescope
- Pressure measured at entrance to control building
[http://mrt-lx3.iram.es/tau/taumeter-main-db.php Taumeter] does regular skydips to inform the observer about the sky transmission near 225 GHz. The local oscillator works at 225GHz. The IF is 1.5GHz and the bandwidth is 0.5GHz. It is a double-sideband Schottky receiver.
[#beginOfPage Back to top]
Old [http://www.iram.es/IRAMES/telescope/telescopeSummary/telescope_summary.html Telescope System Summary page of September 07]
This is page http://www.iram.es/IRAMES/mainWiki/TelescopeSystemSummary moderated by Carsten Kramer