Phase 2 help page

The main goal of Phase 2 is to define how and when the observations required to fulfill an observing proposal need to be done. The definition of the observations is grouped into observation sequences. These sequences contain all the required information that the telescope will use to perform the observations. Phase 2 is designed to provide the observer a way to define one or more sequences through four steps:

  • Step 1. Introduction of targets not defined in Phase 1.
  • Step 2. Introduction of observing constraints.
  • Step 3. Introduction of instrument configurations.
  • Step 4. Definition of sequences with the information provided in previous steps.

The information provided in the Phase 2 forms is continuously saved to the OAdM database and, therefore, a permanent Internet connection is required to fill in the Phase 2 forms. The information provided in Phase 2 can be edited at any time as long the proposal is active. In addition, a given sequence can also be edited at any time as long as it has not been executed. Observations will be queued into the observation plan as soon as the Enabled button is selected in Step 4.

A description of each field is provided. Those fields marked with an asterisk (*) are compulsory.


Targets

The introduction of targets follows the same procedure as the one already used in Phase 1. The observer can introduce any number of desired targets to observe. By default, those targets already introduced in Phase 1 are also present in Phase 2. As in Phase 1, two procedures can be used to introduce new targets: Add target and Add several targets.


Add target

New targets can be introduced one by one by clicking on Add target. Three fields must be filled for each target:

  • Source Name. The name of the target. Any name (either cataloged or not) is valid. This name will be inserted in the FITS header and, therefore, should be shorter than 70 characters.
  • Coordinate type. The type of coordinates to be introduced. Currently, three coordinate types can be selected:
    • Equatorial. To introduce equatorial coordinates with proper motion.
    • Minor planet. To introduce targets having a heliocentric orbit using mean orbital elements.
    • Comet. To introduce targets having a heliocentric orbit using orbital elements at perihelion.
  • Coordinate value. Depending on the coordinate type chosen, a specific format must be introduced. Please, visit the Coordinate formats page for further information. Some examples for each coordinate type are also provided in the Examples page.

Add several targets

When observing a large number of targets is desired, introducing all the targets one by one may become extremely tedious. Therefore, targets can be introduced as properly formatted text by clicking at Add several targets.

Those observers wanting to observe a large field using several exposures (a mosaic), introducing all the subfields is not required, since dithered pointings will be allowed to be introduced at Step 3. Therefore, only one of the pointings is required at this stage.

The Add several targets window basically requests a series of lines (one per target), containing three fields separated by comas. The three fields correspond to the same fields required to introduce targets one by one. However, the coordinate types use acronyms to facilitate their specification. The details of the three fields that must be filled for each target are:

  • Source Name. The name of the target. Any name (either cataloged or not) is valid. This name will be inserted in the FITS header and, therefore, should be shorter than 70 characters.
  • Coordinate type. A letter describing the type of coordinates to be introduced. Currently three coordinate types can be selected:
    • Equatorial (e). To introduce targets in equatorial coordinates (plus proper motion), the letter e should be used as coordinate type.
    • Minor planet (m). To introduce targets having a heliocentric orbit using mean orbital elements, the letter m should be used as coordinate type.
    • Comet (c). To introduce targets having a heliocentric orbit using orbital elements at perihelion, the letter c should be used as coordinate type.
  • Coordinate value. Depending on the coordinate type chosen, a specific format must be introduced. Please, visit the Coordinate formats page for further information. Some examples for each coordinate type are also provided in the Examples page.

Observing constraints

The targets specified at Step 1 should be observed under certain sky conditions. PI can specify any number of observing constraints. These will be matched to particular targets at Step 4.

The list of observing constraints is extended from four at Phase 1 to eight at Phase 2. Among the four Observing constraints specified at Phase 1 (the Sky brightness, the Seeing, the Cloud cover and the Solar elevation), only those constraints requiring less demanding conditions than the ones specified at Phase 1 will be available.


Sky brightness

Specifies the largest sky illumination for an observation to be executed. Two constraints can be selected:

  • Bright. When the Moon is above the horizon with a fractional illumination larger than 30%. Observations with this constraint could also be executed during Dark time specified below.
  • Dark. When the Moon is below the horizon or the fractional illumination is lower than 30%.

Seeing

Specifies the worst seeing value for an observation to be executed. Final seeing values on the astronomical images are used and, therefore, take into account dome turbulence and telescope optics. However, they do not consider airmass effects and it is defined in V band filter. To better understand this value, it can be considered that an exposure is taken pointing at zenith in V band filter. The resulting FWHM is the seeing value. Three seeing constraints are possible:

  • Good. When seeing is below 1.5 arcsec.
  • Medium. When seeing is below 2.5 arcsec.
  • Poor. When seeing is above 2.5 arcsec. This option cannot be selected. Any observations obtained during poor seeing will never be accounted to the proposal time.

Please, note that the good seeing conditions will limit the number of nights to less than 50% of the possible nights. In case that you require different seeing constraints (e.g.: seeing below three arcsec), please send a request using the Contact Form.


Cloud cover

For some scientific projects, excellent sky conditions are not always required and thin veils or clouds are also valid for observation. Therefore, two constraints can be selected:

  • Photometric. The sky must be completely clear.
  • Spectroscopic. Thin veils or cloud can also be present. Observations requesting Spectroscopic time could also be executed during Photometric time.

Solar elevation

The most usual Solar Elevation constraint will be to observe only when the Sun is well below horizon (at Night Time). However, in some cases, observations with some solar illumination might also be allowed. Please, note that this constraint refers only to science images and not to calibration exposures (i.e.: flats). Five constraints can be selected:

  • Night Time. Sun is more than 18 degrees below horizon.
  • Nautical twilight. Sun is more than 12 degrees below horizon.
  • Civil twilight. Sun is more than 6 degrees below horizon.
  • Sunset to sunrise. Sun is below the horizon.
  • Day Time. Sun is above horizon. Special justification is required to observe during this period.

Moon distance

The minimum angular distance to the Moon in degrees. This value is particularly useful when observing in bright sky.


Airmass

The airmass range for observations to be taken. By definition, minimum values must be larger than one.


Hour angle

Some observations, apart from the airmass, may require targets to be close to the meridian or at a certain hour angle. The values specified here should be in hours.


Delay

There are two ways to introduce time constraints in a given observation: Delay and Windows. The Delay fields (before and after) can be used to introduce relative time delays (in hours) between consecutive observations.


It is important to properly distinguish the delays defined for sequences (at Step 4) from the delays defined for Observing constraints (Step 2). Please visit the Examples page for further information.


Windows

In order to specify when a particular observation has to be executed using an absolute time definition, one or several Windows can be defined. By default, all Observing constraints have a Window starting at the date of proposal acceptance (or at the beginning of the semester) and ending at the end of the semester. Additional Windows can be used to specify certain ephemeris (e.g., eclipses, transits, bursts, etc.).

  • Start JD. The time when the Window starts in Julian Days.
  • End JD. The time when the Window ends in Julian Days.
  • Period. For periodic phenomena, specifying all the possible Windows as two Julian Days may become extremely tedious. In order to facilitate this process, the Start JD and the End JD can be used to specify one of the Windows. In case that a period (in days) is also specified, the specified Window will be repeated every Period. In case that no periodicity is desired, a value of 0 should be specified.

In case that several Windows are defined, the allowed execution time will be the intersection of all the Windows. Therefore, the PI should be careful that the resulting Window is large enough to allow the acquisition of all the required images, as defined in Step 3. Some Window examples are provided in the Examples page.

Instrument configurations

Each target requires an instrumental configuration to be observed. Any number of Instrument configurations can be defined. These will be matched with Targets and Observing constraints at Step 4.


Instrument

Two instruments can be selected: MEIA3 and ARES. For technical reasons, LAIA is called MEIA3 in MUR. Please, visit the instrumentation web page for further information.


Target type

The type of images to be taken. When including calibration images, these will be considered part of the proposal and, therefore, the time required to complete them will be charged to the proposal time. In case that no calibration images are defined, the calibration images taken during the standard calibration procedure for each instrument (LAIA/MEIA3 and ARES) will be provided. Currently, four types of images can be taken:

  • Bias. Images with zero exposure time and shutter closed.
  • Dark. Images with the shutter closed, but with a given exposure time.
  • Sky flats (LAIA/MEIA3 only). Uniformly illuminated exposures taken during twilight. Strict sky conditions to be taken during twilight should be defined when taking sky flats. Otherwise, the quality of the observations could be below expectations.
  • Science. This should be the most commonly used type of observation. Most science observations will be taken during night time.

Follow type

In some specific cases, the PI may want to observe an object, not following the object movement, but some other type of movement. Therefore, the telescope tracking can be defined using three Follow types:

  • None. No type of tracking will be performed.
  • Object. The object movement (as defined in the Coordinate type) will be followed.
  • Sidereal. Sidereal tracking, regardless of the celestial motion of the object to be observed. For Equatorial coordinate types, there is no difference between Object and Sidereal.

Dithering

In case that several exposures with slightly different telescope pointings (e.g., to make a mosaic) are required, they can be specified through different Targets, or the Dither fields can be used. The dithers are defined by selecting a Dither pattern, a Dither (RA) and an Dither (Dec). The dither values (in degrees), correspond to the maximum size of the pattern. For further information, some examples are also provided in the Examples page.


Defocus

For bright sources, it may be useful to defocus the telescope. The defocusing amount is automatically determined to avoid saturating the brightest source in the field. In case that defocusing is required, the Defocus check box should be marked. Defocus will be ignored for ARES observations.


Exposures

The number of exposures to be taken when using the current Instrument configuration. All the exposures will be taken consecutively. In case that a Dither pattern is defined, Exposures will be taken for each one of the different pointings defined.


Exposure time

The exposure time for each one of the exposures defined in the current Instrument configuration. An exposure time calculator exists, to estimate the exposure time. Different exposure times should be defined in different Instrument configurations.


In case that non-photometric conditions exist, the Adapt time check box can be marked to allow an increase in the exposure time to reach the desired S/N. The maximum increase in the exposure time will be determined by the need to fit the entire sequence within the specified Windows or the same night.


Binning

Currently, two binnings can be specified for LAIA/MEIA3 and ARES: 1x1 and 2x2. Please, note that binning ARES spectra will result in ~1 pixel per resolution element.


Subframe

Around 8 seconds are required to read the whole LAIA/MEIA3 CCD. In case that a faster read-out is desired, the CCD area to be read can be reduced as desired with a Subframe value (in pixels). The Subframe value is the number of pixels in each direction (rows and columns) to be read around the center of the CCD. The subframe value is applied before binning. So, to read the whole CCD, a default value of 4096 is used (the CCD has 4096x4108 pixels), regardless of the binning used. It is important to remind that the pointing accuracy of the TJO is between 1 and 2 arcminutes (almost 350 pixels). Therefore, a Subframe value smaller than 700 pixels is strongly discouraged.


For ARES, the Subframe option is also offered to cut the desired wavelength range. However, little gain is obtained when using subframe and, therefore, using the default value is recommended.


Filter

Five different filters can be selected for LAIA/MEIA3: U, B, V, R and I. In addition, exposures can also be taken without filter. Please, visit the exposure time calculator to determine the Exposure time for each filter


Two VPHs can be selected for ARES: Red and Green. In addition, the PI can choose whether to include a calibration exposure between the two sky fibers. Three possible calibration exposures can be selected:

  • ThAr. This is likely the most common calibration required. A Thorium-Argon spectrum is obtained together with the science exposure to calibrate the science spectrum in wavelength.
  • LEDS. A LED spectrum is obtained together with the science exposure. This might be useful to calibrate the spectrum continuum.
  • Tungsten. A tungsten spectrum is obtained with the science exposure. This might be useful to calibrate the spectrum continuum.

Sequences

Sequences are the core of the Phase 2 definition. The telescope expects observations to be provided in sequences and therefore, defining sequences is equivalent to queue an observation to be done. Once a sequence is enabled (by checking the Enable button) the sequence will be automatically queued at the telescope without any human interaction. An enabled sequence can be edited at any time, as long it has not been executed at the telescope. After execution, the sequence will be blocked and the PI will no longer be allowed to edit it. Even though, a blocked sequence, can always be disabled (by clicking again the Enable button). Therefore, in case that any sequence is wrongly defined, it can always be disabled.


In order to define sequences, a new model (that we call the TOI model) is used. Each observation involves the combination of three elements: Targets, Observing constraints and Instrument configurations (a TOI). The three elements are designed to tell the telescope: what (Target), how (Instrument configuration) and when (Observing constraint) an observation has to taken. TOIs are the atomic unit for the MUR and telescope system and, therefore, a TOI must fit into all the constraints specified in the corresponding Observing constraints. A complete observing sequence can be defined by combining one or several TOIs.


In addition to TOIs, an observing sequence also requires a certain amount of iterations, with a certain delay between them, to be executed at certain times. All these parameters (explained below) apply to the whole sequence and, contrary to Observing constraints (applied to a single TOI), they treat the whole sequence as a single TOI.


Priority

The PI can define a certain priority in case that two or more sequences of the same proposal can be observed at the same time. By default, a value of zero indicates the minimum possible priority and the PI can increase priority for a sequence without any limit. When several sequences of the same proposal can be executed at the same time, the one having the highest priority will be executed first. It is important not to confuse this priority value with the priority of your proposal. This priority value is designed to define what sequences should be executed first. The priority value of your proposal is defined by the CAT (from 0 to 10) and defines what proposal should be executed preferentially.


Iterations

The number of times that a sequence has to be executed. Any number larger than zero can be used, but the sequence will only be executed when the proposal has some time available. In addition, when the sequence has to be executed as long as there is time available, the "Full time" check box can be marked for this purpose.


Delay

In case that more than one iteration is requested, the minimum time between two successive executions of the same sequence can be specified (in hours). This field is specially useful in case that a sequence has to be executed, for example, once/twice per night/week/month. Please, note that a Delay only specifies that the same sequence cannot be executed with a separation shorter than Delay, but does not guarantee that it will be executed after the Delay.


It is important to properly distinguish the delays defined for sequences (at Step 4) from the delays defined for Observing constraints (Step 2). Please visit the Examples page for further information.


Equation

Equations indicate what to be observed and how. Therefore, they are the most important element of a sequence. The minimum element of an equation is the combination of one Target, one Observing constraint and one Instrument configuration (a TOI). The combination is done by typing a t and a number for a target, an o and a number for the observing constraint and an i and a number for the instrument configuration. Numbers are shown in previous steps of Phase 2. So, to combine the Target number 1 in step 1 with the Observing constraint number 1 in step2 and with the Instrument configuration in step 3, you should write: t1o1i1.


Several TOIs can be related thanks to seven different operators:

  • And (&). The and operator indicates that two (or more) TOIs have to be executed, without specifying the order. They can also be executed leaving a certain amount of time between them. E.g.: t1o1i1 & t2o2i2.
  • Or (|). The or operator indicates that only one among two (or more) TOIs have to be executed. E.g.: t1o1i1 | t2o2i2.
  • After (>). The after operator indicates that two (or more) TOIs have to be executed in a particular order. This basically implies that the second TOI will be executed after the first one is executed. However, a certain amount of time could be left between them. E.g.: t1o1i1 > t2o2i2.
  • Airmass (<). The airmass operator indicates that two (or more) TOIs have to be executed fulfilling specific airmass constraints. This basically implies that the second TOI will be executed at an airmass larger than the first one. E.g.: t1o1i1 < t2o1i2.
  • Parentheses (()). The parentheses can be used to group TOIs. E.g.: t1o1i1 & (t2o2i2 | t3o3i3).
  • Consecutive ([]). The consecutive operator should be used when several TOIs must be executed consecutively. E.g.: [t1o1i1 & t2o2i2] | t3o3i3.
  • Product (*). The product operator indicates how many times a TOI (or a group of TOIs) has to be executed in a sequence. It can also be used to specify a Target, an Observing constraint or an Instrument configuration for several TOIs. E.g.: 3*o1*(t1i1 > t2i2).

In addition, in case that the telescope pointing is not important (e.g., to take bias), the t0 target can be used. This will be interpreted as Point anywhere by the telescope. For additional information, please visit the Examples page.


Required max time and Required min time

In order to better define the observation sequences, a calculator provides the minimum and maximum times required to complete the sequence specified in the Equation field. Times are computed by adding, for each TOI, the corresponding concepts:


  • Telescope pointing: 30 seconds
  • LAIA/MEIA3 filters or ARES/VPH: 30 seconds
  • Exposure time
  • Read-out time: 8 seconds
  • In case of Dithers: 5 seconds per pointing

The minimum time corresponds to the execution of the fewer number of TOIs possible, without considering overheads due to telescope pointing or MEIA2 filter change. The maximum time adds the maximum number of TOIs that can be executed, supposing that the telescope has to be pointed and the filter changed.


Enabled

To submit a sequence to the observatory for execution, the Enabled button must be checked. Sequences can be edited at any time, but no modifications are allowed to already executed sequences. If you want to stop observing a wrongly defined sequence that still has some iterations left, the Enabled button can always be unchecked to disable the sequence.