Early Science
When completed, ALMA will offer 50 antennas in its main array, 16 more in the ALMA Compact Array, a variety of configurations, a large number of observing modes (standard interferometry, mosaicing, fast-switching, etc.) and complete frequency coverage of the mm/submm windows up to 1 THz. However, ALMA will become a powerful, world-beating scientific instrument long before all these capabilities become available. In order to exploit this before the official Inaugration of the telescope, astronomers will be able to apply for time as part of Early Science.
Minimum Requirements for Early Science
Early Science will only proceed once the following requirements have been met:
- Antennas: at least 16 12-m antennas fully commissioned
- Frequency bands: at least three on each antenna
- Array configurations: sufficient pads to cover the shortest spacings and out to a maximum baseline of 250 m
- Observing modes: single-field interferometry
- Correlator modes: a mixture of pseudo-continuum (Time Division Mode) and spectral line (Frequency Division Mode) correlator configurations. Around 20 modes are being commissioned for Early Science, but the highest priority has been given to the modes shown in the table below. See the table below or ALMA Memo 556 for more information on correlator modes
- Calibration: to a level already achieved on established mm arrays
- Software: tools required for proposal submission, preparation and execution of observations and data reduction in place
Once these are met, the Early Science Decision Point (ESDP) will see the release of the very first Call for Proposals to the astronomical community. The deadline for the receipt of proposals (submitted with the ALMA Observing Tool) will be two months after the ESDP and Early Science observations will begin six months after that i.e. eight months after the ESDP. Information on when these will occur can be found in the ALMA timeline.
| Mode | Total Bandwidth |
Number of Spectral Points |
Spectral Resolution |
Polarization |
|---|---|---|---|---|
| 7 | 2 GHz | 4096 | 488 kHz | Dual |
| 9 | 500 MHz | 4096 | 122 kHz | Dual |
| 12 | 62.5 MHz | 4096 | 15 kHz | Dual |
| 18 | 62.5 MHz | 2048 | 30 kHz | Full |
| 70 | 2 GHz | 64 | 31.25 MHz | Full |
Goals for Early Science
In addition to the above minimum requirements, it is planned that the following are also available for Early Science:
- Frequency bands: 3, 6, 7 and 9 on all antennas and 4 and 8 on as many as possible
- Array configurations: additional spacings out to a maximum baseline of 1 km
- Observing modes: interferometric pointed mosaics
- Polarization: linear and circular polarization observations of compact sources
- Single dish: extended sources mappable in either continuum or spectral lines, including On-The-Fly (continuous scanning)
- Calibration: to a level better than already achieved on established mm arrays
The first Call for Proposals will detail exactly what will be available for Early Science.
CSV
CSV activities will continue during Early Science operations which will therefore also require that subarraying (at least two groups of antennas operating independently) is possible.